In this article, the results of three experiments designed to evaluate the impact of an electronic mediator on negotiating behavior are reported. The mediator is a web-based tool that serves three mediation functions: diagnosis, analysis, and advice. The diagnosis provides information about progress toward or away from agreements. The analysis identifies the possible sources of problems in each of several areas of negotiation. The advice is linked to the source of the problem and based on empirical research. In all of the experiments, role-playing negotiators attempted to reach agreement on seven issues discussed in a simulation of a conflict that resembles the pre-war conflict between the United States and Iraq. The first experiment consisted of a comparison between the e-mediation support technology and a condition in which negotiators reflected separately about the negotiation without the technology. Results indicate that access to the technology produced significantly more agreements and resulted in more positive perceptions of the outcomes than the reflection condition. However, perceptions of the between-round periods were more positive for reflection-condition negotiators. In the second experiment, we compared the e-mediation technology with a condition in which negotiators only received the advice in paper form. Access to the technology resulted in more agreements than advice-only, although the differences were smaller than those obtained in the first experiment, and perceptions of outcomes were more positive for advice-only negotiators. The third experiment compared two forms of e-mediation (separate and joint) with a scripted live mediator. Results show that joint e-mediation out-performs live mediation on some measures; both these conditions resulted in more agreements, and more integrative statements, than separate e-mediation. The live mediator was perceived more favorably than both the separate and joint e-mediators. Possible explanations for these results are discussed along with an agenda for further research on e-mediation.