# The Illustrious 18: The Deviations Worth Learning Don Schlesinger's Illustrious 18 are the count-based deviations that deliver most of the playing gain in card counting. What an index play is, the famous examples, and how to learn them in order. Source: https://21trainer.app/articles/illustrious-18-explained/ Updated: August 25, 2026 Publisher: 21 Trainer, makers of Blackjack Strategy: 21 Trainer, an educational blackjack trainer for iPhone and Android (App Store: https://apps.apple.com/app/blackjack-strategy-21-trainer/id6759527695, Google Play: https://play.google.com/store/apps/details?id=app.blackjacktrainer) > **Educational content, not gambling advice.** 21 Trainer and this article teach card counting as a skill, practiced with virtual chips only. No counting system guarantees winnings, and nothing here encourages real-money play. If gambling is a problem for you or someone you know, call 1-800-522-4700 (National Council on Problem Gambling). Every counting student eventually discovers an uncomfortable fact: complete index tables list well over a hundred spots where the count can flip the correct play, and memorizing all of them is a monstrous job with feeble returns. Don Schlesinger's contribution, in his book Blackjack Attack, was to rank the deviations by how much each is actually worth and publish the honest conclusion: eighteen of them deliver the large majority of the available playing gain. The list has been called the Illustrious 18 ever since, and it turned deviation study from a memorization swamp into a short, ordered curriculum. ## What a deviation actually is [Basic strategy](https://21trainer.app/articles/blackjack-basic-strategy-explained/) is the perfect answer to an average shoe. But a counter, by definition, knows when the shoe is not average: a high [true count](https://21trainer.app/articles/running-count-vs-true-count/) means the remaining cards are unusually ten-rich, and that changes the physics of a handful of decisions. Standing on 16 against a 10 is wrong in a neutral shoe, but when tens are thick, the hit busts more often and the dealer's forced draws break more often too; at some point the balance tips and standing becomes right. That tipping point is the index. Each Illustrious 18 entry is a hand, an upcard, and the true count at which the play flips. Below the index you play basic strategy; at or above it, you deviate. Nothing mystical happens: the arithmetic that produced the chart is simply being rerun with the shoe you actually face. ## The famous entries The canonical numbers below are from Schlesinger's published multi-deck, dealer-stands-on-soft-17 list, in Hi-Lo true counts; treat them as the reference shape and verify the exact values for your rules before studying seriously. - **Insurance at +3.** The most valuable deviation by a wide margin, and the whole list's poster child. Basic strategy never insures; a ten-rich shoe makes the dealer's blackjack frequent enough that the 2:1 side bet turns profitable. It ranks first because the spot recurs every time an ace shows. - **Stand 16 vs 10 at 0 or higher.** The most used hand deviation: any positive count flips the game's most notorious decision from hit to stand. - **Stand 15 vs 10 at +4.** The 16's little sibling, needing a richer shoe to tip. - **Split 10s vs 5 at +5 and vs 6 at +4.** The infamous one: breaking a made 20 becomes mathematically right when tens are dense enough that each new hand expects to catch one. Correct, conspicuous, and famously the play that draws the pit's attention. - **Double 10 vs 10 at +4, double 11 vs A at +1, double 9 vs 2 at +1.** Aggressive doubles that a rich shoe unlocks, extending the ladder from our [doubling guide](https://21trainer.app/articles/when-to-double-down/). - **Stand 12 vs 3 at +2, stand 12 vs 2 at +3.** The stiff-hand borderlands, where modest counts push marginal hits to stands. - **Negative-count entries** such as hitting 13 against a 2 or 3 when the count falls below the index: thin shoes turn cautious stands back into hits, a reminder the list runs in both directions. A companion set, the Fab 4, covers the most valuable late-surrender indices (15 and 14 against strong upcards); it belongs to the same family and the same book, and most players learn it immediately after the 18. ## Where deviations rank in the skill stack Honesty requires proportions: bet variation, not play variation, is the engine of counting. Scaling bets with the count produces the clear majority of a counter's edge; the entire Illustrious 18 adds a meaningful but distinctly smaller layer on top, per the published analyses. That ordering dictates the curriculum from our [counting overview](https://21trainer.app/articles/card-counting-explained/): automatic basic strategy, then a flawless count, then the bet spread, and only then indices. A deviation executed off a wobbly count is worse than no deviation at all, because you pay its cost in errors without collecting its premium. The same proportions explain who should bother. A recreational counter practicing for the intellectual sport gets most of the fun from insurance plus the first few entries; the full eighteen is for players pursuing the last increments of theoretical edge. Both are legitimate ways to enjoy the skill; only one requires flashcards in your pocket for a month. ## Learning them for real The list is short, but table execution is a recognition task under load: the count sits at +4, a 15 lands against a 10, and the flip has to fire in the second you have. Study order follows value: insurance first, then 16 vs 10, then down the ranking. Drill each index in isolation until the trigger is reflexive, then mixed, then inside full-speed play with the count running, which is exactly the progression a dedicated deviation trainer automates. And keep the frame the callout above insists on: indices are the graduate seminar of a skill whose every level, per the honest limits in our counting overview, offers a thin edge, thick variance, and casinos entitled to refuse the game. The Illustrious 18 is applied probability at its most elegant; learn it because the machinery is beautiful, and let that be the payoff. ## Frequently asked questions ### What is the Illustrious 18 in blackjack? It is Don Schlesinger's ranked list, published in Blackjack Attack, of the eighteen count-based strategy deviations that deliver the large majority of the playing gain available to a card counter. Each entry names a hand, a dealer upcard, and an index: the true count at which the correct play flips from the basic strategy answer to an alternative. ### What is an index play or deviation? A deviation is a spot where the count overrides basic strategy. Basic strategy assumes an average deck, but a strong count means the remaining shoe is unusually rich or poor in high cards, and for a small set of hands that changes the best action. The index is the trigger: reach that true count and you switch plays; below it, basic strategy stands. ### What is the most important deviation to learn first? Insurance, at a Hi-Lo true count of about +3, per Schlesinger's published list. Basic strategy refuses insurance always, but a ten-rich shoe pushes the dealer's blackjack odds past the break-even point, making the side bet profitable. It tops the ranking because the situation arises every time the dealer shows an ace, far more often than any single hand combination. ### Do deviations matter more than bet spreading? No. Varying bets with the count produces the clear majority of a counter's total edge; the full Illustrious 18 adds a meaningful but smaller slice on top. That is why the learning order is fixed: automatic basic strategy first, then an accurate count, then bet spreading, and only then deviations. Indices layered onto a shaky count subtract value rather than add it. ### Are the Illustrious 18 index numbers the same at every table? No. The canonical numbers were computed for multi-deck games with the dealer standing on soft 17, and they shift with rules, deck count, and the counting system in use; H17 games and single-deck games use somewhat different values, and unbalanced counts like KO use their own. Learn indices from a source computed for your rules and system, and verify against the published lists. ## Keep reading - [How Card Counting Actually Works](https://21trainer.app/articles/card-counting-explained/) - [The Hi-Lo Count: The System Most Counters Learn First](https://21trainer.app/articles/hi-lo-card-counting/) - [Running Count vs True Count](https://21trainer.app/articles/running-count-vs-true-count/)