Our experiment tests the pricing and cartel deterrence effects of three different cartel fining regimes: fines based on cartel profits, cartel revenues, and cartel overcharge. Subjects play an infinitely repeated Bertrand triopoly game. In each period, subjects first engage in optional communication and then set their price unilaterally. Next, the market clears, and communication is detected and punished with a fixed probability of 0.2. We vary fines across different treatments by basing them either on a firm’s revenue, profit, or overcharge. Finally, subjects receive feedback on the prices, fines, and profits. With probability 0.9, the three matched subjects play another period, while with probability 0.1, each subject is re-matched with two new subjects before playing the next period.