The effectiveness of three mediation tactics was compared in two laboratory studies. It was hypothesized that a content mediation procedure which involved identifying the priorities of both parties and suggesting a trade-off of low for high priority issues would be most effective in helping to resolve the dispute, followed by an issue identification mediation procedure in which priorities were identified but no suggestions were made. A positive framing mediation procedure in which the benefits of a negotiated settlement were emphasized was expected to be somewhat less effective. In Study 1, 64 students played the role of company negotiator and interacted with a programmed citizen group negotiator. All three mediation tactics produced more satisfactory outcomes (higher joint payoffs) than did a no-mediation condition. In Study 2, 46 pairs of students negotiated with one another and received content mediation, issue identification mediation, positive framing mediation, or no mediation. Negotiators receiving content mediation achieved more satisfactory outcomes (higher joint profits) than did negotiators in the other 3 conditions. Results are discussed in terms of a contingency model of mediation effectiveness.