The Illustrious 18 is Don Schlesinger’s list of the 18 most valuable basic strategy deviations for card counters, ranked by their total contribution to expected value. Learning them adds roughly 0.1% to 0.2% to a counter’s edge on top of betting variation. They are the layer that sits between basic strategy and full professional play.
What the Illustrious 18 Are
Basic strategy assumes a neutral shoe: every card equally likely, every decision optimised for that assumption. When a counter knows the shoe has shifted (positive count means more tens and aces remaining; negative count means the opposite), certain basic strategy decisions become wrong. The plays that should change, and the count threshold at which they should change, are called deviations or index plays.
Don Schlesinger published the canonical list in Blackjack Attack (1997, with multiple editions since). He calculated the value of every plausible deviation using a metric he called SCORE (Standardised Comparison Of Risk and Expectation), which weights each deviation by how often the situation arises and how much EV the deviation captures when it does. The 18 highest-SCORE plays became the Illustrious 18: the deviations that deliver the most edge per memorisation effort.
For a working counter using Hi-Lo, learning the Illustrious 18 adds roughly 0.1% to 0.2% to total expected value, on top of the betting advantage from spreading bets to the count. That sounds small but compounds: it represents most of the available deviation EV (the next 20 deviations together add less than one more 0.1%), at a fraction of the memorisation effort of learning the full deviation chart.
How Deviations Work
A deviation is just a basic strategy play that becomes wrong above (or below) a specific true count threshold, called the index number. For example, the basic strategy chart says to hit hard 16 against a dealer 10. The Illustrious 18 says: at true count 0 or higher, stand instead. The index number for this play is 0.
Below the index, you play basic strategy. At or above the index, you make the deviation. That is the entire system. The hard part is memorising 18 different player-hand / dealer-card combinations and the specific count threshold for each.
Reading the index numbers
Most deviations trigger at a positive count threshold (you make the deviation when the count reaches the index or goes higher). A few trigger at a negative threshold (you deviate when the count drops to the index or lower). Both directions are noted in the list. Index numbers assume a 6-deck S17 game with Hi-Lo counting; small adjustments apply for other rule sets, but the directional logic does not change.
The Illustrious 18
Ordered by approximate SCORE (most valuable first), for a 6-deck S17 game using Hi-Lo:
| # | Hand vs Dealer | Basic Strategy | Deviation | Index |
|---|---|---|---|---|
| 1 | Insurance (any hand, dealer A) | Decline | Take insurance | +3 or higher |
| 2 | Hard 16 vs 10 | Hit | Stand | 0 or higher |
| 3 | Hard 15 vs 10 | Hit | Stand | +4 or higher |
| 4 | Pair of 10s vs 5 | Stand | Split | +5 or higher |
| 5 | Pair of 10s vs 6 | Stand | Split | +4 or higher |
| 6 | Hard 10 vs 10 | Hit | Double | +4 or higher |
| 7 | Hard 12 vs 3 | Hit | Stand | +2 or higher |
| 8 | Hard 12 vs 2 | Hit | Stand | +3 or higher |
| 9 | Hard 11 vs A | Hit | Double | +1 or higher |
| 10 | Hard 9 vs 2 | Hit | Double | +1 or higher |
| 11 | Hard 10 vs A | Hit | Double | +4 or higher |
| 12 | Hard 9 vs 7 | Hit | Double | +3 or higher |
| 13 | Hard 16 vs 9 | Hit | Stand | +5 or higher |
| 14 | Hard 13 vs 2 | Stand | Hit | -1 or lower |
| 15 | Hard 12 vs 4 | Stand | Hit | 0 or lower |
| 16 | Hard 12 vs 5 | Stand | Hit | -2 or lower |
| 17 | Hard 12 vs 6 | Stand | Hit | -1 or lower |
| 18 | Hard 13 vs 3 | Stand | Hit | -2 or lower |
The pattern: most deviations are positive-count plays where extra tens make stiff hands more dangerous (so you stand) and double-down opportunities more profitable (so you double or split). A handful are negative-count plays where the shoe is rich in low cards, dealer busts are less common, and you have to hit your own stiff hands rather than relying on the dealer to bust.
The Top Three, Explained
The top three deviations carry roughly 60% of the total value of all 18. If you learn nothing else, learn these.
Insurance at +3 or higher. The single most valuable deviation in counting. At true count +3, the shoe contains enough tens that the dealer’s blackjack probability crosses the 33.3% break-even threshold for the insurance bet. Below +3, insurance is the 7.4% house-edge sucker bet covered in our side bets guide. At +3 it becomes positive expected value, and it remains positive at higher counts. This deviation alone accounts for roughly 30% of the total Illustrious 18 value.
Hard 16 vs 10 at TC 0 or higher. The most common Illustrious 18 situation by frequency. Basic strategy hits this hand because hitting loses less often than standing in a neutral shoe. At true count 0 or above (which includes a meaningful share of all hands you will see), enough tens remain that the dealer is more likely to make a hand and your draws are more likely to bust. Standing becomes correct. The deviation comes up often enough that it carries roughly 15% of the total Illustrious 18 value despite each occurrence being modest.
Hard 15 vs 10 at TC +4 or higher. A higher-threshold version of the same logic as 16 vs 10. Less frequent than the 16 vs 10 deviation but each occurrence captures more EV. Roughly 10% of total Illustrious 18 value.
The Fab 4 Surrender Deviations
The Illustrious 18 list does not include surrender plays because surrender is not available at every table. For tables that do offer late surrender, Schlesinger published a companion set called the Fab 4: the four most valuable surrender deviations, ranked by SCORE.
| # | Hand vs Dealer | Basic Strategy | Deviation | Index |
|---|---|---|---|---|
| 1 | Hard 14 vs 10 | Hit | Surrender | +3 or higher |
| 2 | Hard 15 vs 9 | Hit | Surrender | +2 or higher |
| 3 | Hard 15 vs 10 | Surrender | (already on basic chart) | any positive count strengthens |
| 4 | Hard 15 vs A (H17) | Hit | Surrender | -1 or higher |
If your table offers surrender, learn these alongside the Illustrious 18; the additional EV is meaningful. If your table does not offer surrender, you cannot use them. Full surrender mechanics, including the signal and basic surrender chart, are covered in our surrender guide.
How to Learn the Deviations
The deviations are the last thing you add to your counting toolkit, not the first. The right order:
- Master basic strategy first. Without it, deviations are meaningless. Every deviation is “deviate from basic strategy when…”; if basic strategy is not automatic, you have nothing to deviate from.
- Master Hi-Lo counting and true count conversion. The deviations require accurate true counts in the moment. Approximate counts produce approximate deviation results, which is worse than playing pure basic strategy. The full system is covered in our card counting guide.
- Add deviations one at a time, in SCORE order. Start with insurance at +3. Play with that single deviation added for a week. Then add 16 vs 10. Another week. Then 15 vs 10. Layering them avoids the failure mode of trying to learn all 18 simultaneously and getting most of them wrong.
- Drill on RNG demo tables with the chart visible. Look up every deviation situation as it appears until the recall is automatic. The same RNG drill that builds basic strategy works for deviations.
- The Fab 4 surrender deviations come last, only if you play surrender tables regularly.
Realistic timeline: roughly two months of consistent practice from beginner to confident Illustrious 18 deployment, on top of the time required to learn basic strategy and counting first. Many counters never bother with deviations beyond insurance and 16 vs 10, accepting the small EV loss in exchange for lower mental load.
H17 Adjustments
The index numbers above assume S17 (dealer stands on soft 17). H17 (dealer hits soft 17) shifts a small number of deviations:
- Insurance: threshold drops slightly, take at +2.5 or higher. In practice, still treated as +3.
- 11 vs A: double is already correct under H17 basic strategy. The deviation becomes “double at any count” rather than “double at +1 or higher.”
- 10 vs A: index drops to +3 instead of +4.
- 9 vs 2: index stays at +1.
The H17 adjustments are minor. A counter playing both S17 and H17 tables can use the S17 index numbers throughout with negligible EV loss; the directional decisions are identical.
Common Mistakes
- Memorising the running count threshold instead of the true count threshold. “Stand on 16 vs 10 when the count is +6” is wrong if the shoe has 6 decks remaining (true count is +1, do not stand). The index is always a true count, never a running count. Convert before comparing.
- Deviating before having the count. The deviations only work if your count is accurate. New counters often try to “feel” when to deviate (“the shoe seems hot, maybe I should stand on 16 vs 10”). Without an actual count, you are guessing, and guessing is worse than basic strategy.
- Learning all 18 at once. Trying to memorise the full list before deploying any of it usually results in confusion and slow play. Layer them in order; let each one become automatic before adding the next.
- Ignoring the negative-count deviations (#14 to #18). These come up less often than the positive-count plays but they matter. A counter who only uses the positive-count deviations leaves measurable EV on the table.
- Using deviations as camouflage. Some players deliberately make “wrong” deviation plays to avoid looking like a counter. This costs more EV than it saves heat (because the floor staff watching you do not actually know which plays are deviations). Play correctly; rely on bet spread and demeanour for camouflage instead.
Beyond the Illustrious 18
Schlesinger and others have calculated full deviation charts containing 100+ index plays. The additional deviations beyond the 18 together add less than 0.1% to total EV; for most counters, the memorisation effort outweighs the gain.
A common middle-ground extension is the Illustrious 18 plus the Fab 4 (covered above), which is the standard “complete” deviation chart for serious recreational counters. Beyond that, the most-cited next additions are deviations for soft hands (soft 18 vs ace, soft 19 vs 6) and a handful of additional pair-splitting plays.
The honest cost-benefit: for almost every counter, the Illustrious 18 plus Fab 4 captures essentially all the available deviation EV that justifies the learning cost. Going deeper is for full-time pros.
Frequently Asked Questions
Do I need to know all 18 deviations to benefit from counting?
No. Insurance at +3 alone captures roughly 30% of the total Illustrious 18 value. Adding 16 vs 10 stand at 0+ adds another 15%. Just those two deviations, combined with accurate counting and a reasonable bet spread, deliver most of the available deviation EV. The remaining 16 deviations add increasingly small slices on top.
Are the index numbers the same for every blackjack game?
Close, but not identical. The index numbers above are calibrated for 6-deck Hi-Lo with S17. Single-deck games and H17 games shift the indexes slightly. The shifts are small enough that the same indexes work across most common game types with negligible EV loss; if you play a specific niche game seriously, look up indexes calibrated to that ruleset.
Why does insurance work at TC +3 but not at lower counts?
Mathematics. Insurance pays 2:1 if the dealer has blackjack, so it requires the dealer to have blackjack more than one-third of the time (33.3%) to break even. In a neutral shoe, that probability is roughly 30.9%, well below break-even. At true count +3, the shoe has enough additional tens that dealer-blackjack probability crosses 33.3%, and the bet becomes positive expected value. Each additional point of true count adds further player edge.
If I forget a deviation in the moment, what should I do?
Play basic strategy. Basic strategy is always at most a small loss compared to the correct deviation; an inaccurate guess at the deviation can be much worse. Better to leave 0.1% of deviation EV on the table than to play a “deviation” you cannot remember accurately. If you are forgetting deviations regularly, that is a signal to drill them more before adding additional ones to your active list.
Can I use the Illustrious 18 with counting systems other than Hi-Lo?
Not directly. The index numbers above are calibrated to Hi-Lo. Other counting systems (KO, Hi-Opt I, Hi-Opt II, Wong Halves) have their own index numbers, published in their system-specific literature. The deviation situations are the same; the count thresholds shift to match each system’s count-value scale.
Why are the Fab 4 surrender deviations listed separately?
Because surrender is not offered at every table. Schlesinger split the surrender deviations into a separate list so counters at no-surrender tables can ignore them entirely. For tables that do offer surrender, the Fab 4 deliver additional EV roughly equivalent to the bottom half of the Illustrious 18.
Deviations sit on top of card counting and basic strategy, not as a replacement for them. If counting is not yet automatic, learn that first; deviations without an accurate count are just expensive guesses. For the broader landscape of edge-finding techniques, our advantage play guide covers shuffle tracking, hole carding, and the techniques beyond counting. For the historical context (Schlesinger, Thorp, the MIT teams), see our blackjack history guide. Back to the full Blackjack guide.