The D'Alembert betting system is a simple method to use that does not involve keeping records of which bet was previously placed.  In this system, following a win, a player reduces the next wager by one unit and following a loss the player increases the amount of the wager by one unit.  Each time, the amount of the next bet depends on the result of the previous round.

• Considered as a negative progressive system, the D'Alembert betting system helps a player to keep a hold onto profits once obtained.  After a win, the placer reduces the betting amount thereby eliminating the possibility of losing all of the player's bankroll.
• Compared to some other systems such as the Martingale, the D'Alembert betting system is a slow method and offers a more careful approach to the game.  The slower pace involved with this system enables the player to begin with a higher betting amount, if desired.
• The D'Alembert betting system is used for even money bets.
• Originally used for the game of roulette, today the D'Alembert betting system is popular at the roulette table and also in the game of baccarat.
• The D'Alembert betting system helps a player to recover losses.
• The whole thinking behind this method is that following a win it is assumed that it is less likely that the player will win again and therefore the bet amount is reduced.
• The D'Alembert betting system is probably considered as the most well-known out of all the roulette systems.
• An advantage of using this system is that if a player has a positive bankroll in the middle of a game, the decision may be taken to stop the game and therefore receive the winnings.
• A possible flaw in this system is that the random element to the particular game means that the possibility of a win following a win depends on luck.

To conclude, the D'Alembert betting system is a progressive betting method.  In this system, the player decreases the size of a bet that follows a win and reduces the size of a bet that follows a loss.  The theory behind this method is that betting more after a loss may recover the money previously lost.