The Illustrious 18: The Key Counting Deviations

The Illustrious 18 is a list of the eighteen most valuable strategy deviations in card counting, popularized by the gambling author Don Schlesinger. Each one tells you to depart from basic strategy when the true count crosses a specific number, called an index. Together they capture most of the extra value that playing deviations can add on top of your betting. Insurance is the single most valuable play on the list, which is why counters learn it first.

What is the Illustrious 18?

The Illustrious 18 is a curated set of the eighteen highest-value playing deviations for card counters, assembled and popularized by Don Schlesinger in his writing on blackjack. A deviation is a play that differs from basic strategy because the count tells you the deck composition has shifted. There are hundreds of possible deviations, but their values vary enormously, and most add almost nothing. The insight behind the list is that a small handful account for the large majority of the gain, so a player can learn just those eighteen and capture nearly all the benefit of a full index chart. This makes the list a practical shortcut: instead of memorizing endless numbers, you focus on the plays that actually move your bottom line. It is one of the most useful ideas in applied card counting.

What is an index number?

An index number is the true count at which a particular deviation becomes the better play. Basic strategy assumes an average deck, but as the count rises or falls the correct decision for some hands changes. The index marks the tipping point. For example, a play might have an index of plus four, meaning you make the basic-strategy move until the true count reaches plus four, then switch to the deviation at that count or higher. Some indexes are negative, telling you to deviate when the count drops below a certain level. To use the Illustrious 18 you memorize each play alongside its index, then compare your running true count to that number in real time. The index is what connects your count to a concrete change in how you play the hand.

Why insurance tops the list

Among all eighteen plays, taking insurance is the single most valuable deviation, and it is usually listed first. There are two reasons. First, the decision comes up frequently, since the dealer shows an ace often over a session, so any edge on it compounds quickly. Second, the swing between the right and wrong choice is large, because insurance pays two to one and becomes clearly profitable once the deck is rich in tens. The insurance index sits at about plus three in common games: below it you decline, at or above it you take insurance. Because it is both common and high impact, many counters consider mastering the insurance index alone to be worth more than most of the other deviations combined. If you learn only one play from the list, learn this one.

How deviations differ from basic strategy

Basic strategy is a fixed chart that gives the best play for every hand assuming a fresh, average deck, and it cuts the house edge to roughly half a percent. It never changes, regardless of what cards have come before, because it is designed for the long-run average. Deviations are different: they only make sense when you know the deck has drifted from that average, which requires counting. A counting deviation says, in effect, that the deck is no longer average right now, so the usual best play is no longer best. This is why deviations belong only to counters. A player who does not track the cards has no way to know when a deviation applies and should stick rigidly to basic strategy, which remains the correct foundation beneath every index play.

Examples of common index plays

The Illustrious 18 covers a mix of hitting, standing, doubling, and splitting decisions. Without reproducing a full chart, here are the kinds of plays it includes, each with its own index the true count must cross:

• Taking insurance when the true count is high enough, the top play on the list.
• Standing on a hard sixteen against a dealer ten once the count reaches the relevant index, rather than hitting.
• Standing on a hard fifteen against a dealer ten at a sufficiently high count.
• Doubling totals such as ten or eleven against strong dealer cards when the count favors it.
• Splitting tens against a weak dealer card at very high counts, a rare but profitable move.

The exact indexes depend on the system and the rules, so learn them from a reliable chart matched to your game.

How much do deviations add to your edge?

Playing deviations add value, but it is important to keep the size honest. For most players, the bulk of a counting edge comes from betting more when the count is high and less when it is low, not from deviations. The Illustrious 18 adds a modest increment on top of that, refining individual decisions when the deck is unusually rich or poor. In many games the full set of playing deviations contributes only a fraction of a percent to the overall edge, though insurance carries a disproportionate share of that gain. This is why the list is designed as the vital few rather than the trivial many. Deviations are worth learning once your betting and basic strategy are solid, but they are the polish, not the foundation, of a winning approach.

How to learn them without errors

Because the whole point of the Illustrious 18 is precision, learn it carefully and in order of value. Start with insurance, since it delivers the most, then add the standing deviations against a dealer ten, which come up often. Use flash cards pairing each play with its index, and drill until the number surfaces instantly when the situation appears. Practice alongside your counting so you are converting to a true count and checking it against an index in one smooth motion, not two separate efforts. Always confirm your indexes match your counting system and the specific rules you play, since numbers from one source may not fit another. Above all, do not let deviations distract you from an accurate count and clean basic strategy, which matter far more.

Should beginners bother with the Illustrious 18?

Not at first. A beginner should build the foundation in order: flawless basic strategy, then an accurate counting system like Hi-Lo, then disciplined bet sizing based on the true count. Only once those are automatic does it make sense to add deviations, and even then the smart approach is to start with just the most valuable few. Learning insurance and a couple of the standing plays captures a large share of the benefit without overloading you. Trying to memorize all eighteen indexes while still shaky on the count usually backfires, because errors in the core count cost far more than any deviation can recover. Grow into the Illustrious 18 gradually, and treat it as a refinement you earn rather than a starting requirement.

Frequently asked questions

What is the Illustrious 18?

It is a list of the eighteen most valuable playing deviations for card counters, popularized by author Don Schlesinger. Each tells you to depart from basic strategy when the true count crosses a specific index number. The list captures most of the value that deviations can add, so counters can skip memorizing hundreds of minor plays.

Which deviation is the most valuable?

Taking insurance is the single most valuable play on the list. It comes up often, since dealers show an ace frequently, and the payout swing is large. The insurance index is about plus three in common games: decline below it, take insurance at or above it. Many counters learn this play before any other.

What is an index number in card counting?

An index number is the true count at which a deviation becomes the better play. You follow basic strategy until your true count reaches the index, then switch to the deviation. Some indexes are negative, meaning you deviate when the count falls below them. Each play in the Illustrious 18 has its own index.

Do beginners need to learn deviations?

No. Beginners should master basic strategy, accurate counting, and bet sizing first, since those provide the bulk of the edge. Deviations are a refinement added later, and even then it is best to start with the most valuable few, like insurance. Errors in the core count cost more than deviations can recover.