Don Schlesinger's complete deviation reference — the 18 highest-value index plays plus the 4 surrender deviations. Sourced from Blackjack Attack, verified against Wizard of Odds. The math says: memorize these 22 plays and you've captured 97% of the gain available from full index play.
Indexes are calibrated for Hi-Lo, 6-deck shoe, S17, late surrender. Sourced from Blackjack Attack by Don Schlesinger.
The 18 highest-value count-based deviations from basic strategy, ranked in order of EV gain.
| # | Play | TC | Action | The logic |
|---|
When late surrender is offered, these 4 deviations capture the highest additional EV. Surrender if true count meets or exceeds the index.
| # | Play | TC | Action | The logic |
|---|
If you only memorize six deviations, make them these. They capture more than half of the total deviation value.
Wizard of Odds simulations using CVCX Blackjack Analyzer (6 decks, S17, surrender, DAS, 4.5-deck penetration, 1-to-15 spread):
Source: Wizard of Odds Hi-Lo statistics, CVCX Blackjack Analyzer simulation data.
Basic strategy assumes a fresh, neutral deck. Card counting tells you when the deck has shifted away from neutral — when it's rich in 10s and aces (favors player) or rich in low cards (favors dealer). When that shift gets large enough, the optimal play for a given hand changes. Deviations are the rules for when to deviate from basic strategy based on the count.
Don Schlesinger ranked every possible deviation by expected value gain in his book Blackjack Attack. The top 18 (the "Illustrious 18") plus the 4 surrender plays (the "Fab 4") capture about 97% of the gain available from full index play. The other 200+ deviations contribute almost nothing — memorizing them is mostly mental load with little payoff.
The Illustrious 18 splits into two types:
The negative-correlation plays feel weird at first because you're hitting hands that look like they should stand. The math says otherwise.
Insurance at TC +3 or higher is the single highest-EV deviation, by a wide margin. Here's why: at TC +3, the deck is rich enough in 10s that the dealer's hole card has more than a 33% chance of being a 10. Insurance pays 2:1, so anything above 33.3% probability of a 10 makes the bet correctly +EV. At neutral counts, the dealer's hole card is a 10 only about 30% of the time — so insurance loses about 7% per bet on average for non-counters. The count flips this from a sucker bet into a money-maker.
Schlesinger used computer simulations of millions of hands at every possible true count, computing the expected value of each available action. The "index number" for a given play is the true count at which the EV ranking flips between two actions. For 16 vs. 10, basic strategy says hit at low counts and stand at high counts — the EV-flip point is at TC 0. For insurance, the flip is at TC +3.
Modern verification with QFIT and CVCX simulators produces the same indexes. The numbers haven't moved meaningfully since Schlesinger published them in Blackjack Attack.
For a counter playing a 6-deck game with a 1-to-15 spread and decent penetration, basic strategy alone (no deviations) actually loses money — the bet spread isn't enough to overcome the house edge without index play. Adding the Illustrious 18 plus Fab 4 brings the edge to about +0.83%. At $25 minimum and 80 hands per hour, that's roughly $50/hour expected value. Half the year of a serious counter's earnings comes from deviations.
Once you've nailed basic strategy, picked a counting system, can convert true count under pressure, and have the Illustrious 18 + Fab 4 memorized — you've assembled the complete card counter's toolkit. From here, the work is practice (drilling counts at speed under pressure) and game selection (finding deeply-penetrated, beatable shoes). The basic strategy chart, counting systems comparison, and true count calculator are all linked together as one suite — go back and forth as needed.
The questions counters ask about index plays and Schlesinger's deviation list.
The Illustrious 18 is a list compiled by Don Schlesinger in his book Blackjack Attack of the 18 most-impactful basic-strategy deviations based on the count. They cover insurance, when to stand on a stiff hand against high dealer cards, when to double on borderline totals, and when to take normally-bad plays the count makes profitable. Memorizing the Illustrious 18 captures roughly 80–85% of the gain available from full index play.
The Fab 4 is Don Schlesinger's companion list of the 4 highest-value late-surrender deviations based on the count: 14 vs. 10 (TC +3), 15 vs. 10 (TC 0), 15 vs. 9 (TC +2), and 15 vs. A (TC +1). Surrender on its own gets underused even by experienced players, but at high counts it stops being a half-loss and becomes the highest-EV available action.
Each index number is the true count threshold at which you deviate from basic strategy. For positive-correlation deviations (most of the list), you take the deviation action when true count is at or above the index. For negative-correlation deviations (items 14 through 18 of the Illustrious 18), you take the deviation when true count is below the index. The index number is in true count, not running count — convert first.
Insurance at true count +3 or higher, by a wide margin. It is the single most-impactful index play and is the only one many casual counters bother to learn.
The next four most valuable are 16 vs. 10 at TC 0, 15 vs. 10 at TC +4, doubling 10/10 vs. 5/6 at TC +5/+4, and standing on 12 vs. 3 at TC +2. The top 6 deviations capture more than half of the total deviation value.
Yes. Don Schlesinger's published indexes assume the Hi-Lo counting system, 6-deck shoe, and standard liberal Vegas rules. They translate roughly to KO and Red 7 with adjustments for the unbalanced count. Higher-level systems like Hi-Opt II have their own index numbers — typically larger in magnitude because the count itself runs higher. If you use a level-2 or level-3 system, look up the system-specific Illustrious 18 in Stanford Wong's Professional Blackjack.
For a typical 6-deck game with a 1-to-15 spread and 4.5-deck penetration, the published Wizard of Odds simulations show: playing basic strategy plus the Illustrious 18 plus Fab 4 gives a player advantage of about 0.834%. Playing all index numbers gives about 0.862%. So the Illustrious 18 plus Fab 4 captures roughly 97% of the total deviation value. Memorizing all 200+ index numbers gains you almost nothing additional.
No. Insurance is a side bet that loses about 7% of its value when you have no count information. The only time insurance becomes profitable is when the deck has a high concentration of 10-value cards. The Illustrious 18 sets that threshold at true count +3 — at TC +3 or higher, take insurance. At TC below +3, decline. Basic strategy players (no counting) should always decline insurance.
Items 14 through 18 of the Illustrious 18 are negative correlations — you deviate to hitting at low counts when basic strategy says stand. The logic is that a low count means fewer 10s remain, so hitting a stiff hand is safer (less likely to bust on the next card) and the dealer is less likely to bust on their stiff. These deviations feel counterintuitive because you're hitting hands that look like they should stand. Most counters learn the positive-correlation deviations first and add the negatives only after the positives are automatic.