Definition
En Prison is a special rule in some versions of French Roulette that applies to even-money bets (Red/Black, Odd/Even, High/Low) when the ball lands on zero. Instead of losing the bet immediately, the player’s wager is “imprisoned” for the next spin to determine if it is returned or lost.
In context
You place $100 on Red and the ball lands on 0. Under the En Prison rule, your $100 stays on the table for the next spin. If Red hits on that next spin, you get your $100 back (no profit). If Black hits, the house takes it. If 0 hits again, the bet usually stays “in prison” or is handled by specific house rules.
Why it matters
En Prison is one of the most player-friendly rules in any casino. It effectively cuts the house edge on even-money bets in half. In a standard single-zero game, the edge is 2.70%, but with En Prison, it drops to 1.35%, making it one of the “best bets” on the casino floor.
Related terms
In detail
“En Prison” literally translates to “in prison.” It is a rule that serves as a sort of “second chance” for the player, mitigating the sting of the zero. In American Roulette, which features both a 0 and a 00, hitting either green pocket means all even-money bets are lost instantly (an edge of 5.26%). In European or French Roulette, the single zero is already better for the player (2.70% edge). But when you add the En Prison rule, the game becomes one of the most mathematically fair options in the house.
How It Works Step-by-Step
- The Bet: A player places an even-money bet (let’s say $10 on “Even”).
- The Zero: The ball lands on 0.
- The Imprisonment: The dealer places a small marker on the $10 bet to indicate it is “En Prison.” The player cannot take the money back; it is locked.
- The Resolution: The wheel is spun again.
- If the next result is “Even” (the original bet), the $10 is released. The player gets their $10 back but wins no profit.
- If the next result is “Odd” (the opposite), the house wins the $10.
- If the next result is 0 again, house rules vary. Sometimes the bet stays in prison, sometimes it is lost, and sometimes a “double imprisonment” occurs.
En Prison vs. La Partage
These two terms are often confused. La Partage is a simpler version of this rule. Under La Partage, if the ball hits 0, the dealer immediately gives you half your bet back and takes the other half.
- La Partage is “half back now.”
- En Prison is “all or nothing on the next spin.”
Mathematically, they result in the same house edge (1.35%). However, En Prison has slightly higher variance because you could win the whole bet back or lose the whole thing, whereas La Partage is a guaranteed 50% loss.
Where to Find It
You will almost never find En Prison in an American casino. Even in Las Vegas, the “high limit” rooms that offer “European Roulette” usually use the La Partage rule instead. En Prison is primarily found in high-end European casinos, specifically in Monte Carlo or parts of France and Germany.
Strategy Implications
If you are a serious roulette player, searching for a table with En Prison (or La Partage) is the single most effective “strategy” you can employ. Systems like the Martingale (doubling after a loss) are slightly safer on these tables because the zero doesn’t wipe you out instantly. It gives the player more time at the table for the same amount of bankroll.
The “No-Spin” Reality
Casinos hate offering En Prison because it kills their profit margin. A 1.35% house edge on a table game is exceptionally low—approaching the edge of a good Blackjack game but without the player needing to learn any complex strategy. The rule exists mostly as a tradition in “Old World” casinos to maintain a sense of elegance and fairness. For the operator, the “In Detail” truth is that this rule is a marketing expense; they sacrifice house edge to attract high-stakes players who wouldn’t play on a “greedy” American 5.26% wheel.