One of the often-misunderstood rules of casino Blackjack, this side bet against the Dealer having a Blackjack allows you to cut your losses -- but only in the event the Dealer has an Ace showing.

"Insurance" is offered only when the Dealer's face-up card is an Ace. This phase of play occurs before the the Dealer checks to see if he or she has a Blackjack and before the players take their turns. Going from the Dealer's left and around the table, each player is asked, "Would you like Insurance?". If the player choses to take the offer, she or he places an amount equal to one-half the original bet on the table. Once all players have decided, the Dealer checks for a Blackjack. If the Dealer has one, the players who "purchased" Insurance receive a 2:1 payoff on the side bet, but lose the initial bet (adding everything together, the entire hand turns into a Push for the player). Otherwise, play continues as usual.

With completely even distribution, the odds of the Dealer having a Blackjack when the face-up card is an Ace are approximately 8%. It becomes very advantageous to keep track of the number of 10s left in the deck in this case.