Parlay System is a positive progression system similar to the Paroli System. It is also known as the "Let It Ride" system. It is one of the oldest and the simplest betting systems. It is based on pyramiding your profit. You use your original stake and your winning profit (or some part of it) to place then next bet with (of course only in the case of winning the first bet). Example: You bet 1 USD. You win 2 USD. You bet 2 USD. You win 4 USD. You bet 4 USD. You win 8 USD. And so on...