Abstract: Mediation caucusing — that is, separate meetings conducted by the mediator with some, but not all, of the parties — is widely used, but it has become increasingly controversial, as some mediators advocate for a no-caucus form of mediation using only joint sessions with all parties present. The rationale for the no-caucus model is that caucuses give the mediator too much power at the expense of the parties, and joint sessions improve the parties' understanding of each other's views. But caucusing adds value to mediation in several ways. First, from the standpoint of economic theory, caucusing provides mediators with an important tool for overcoming two impediments to settlement — the “prisoner's dilemma” (caused by the parties' fear of mutual exploitation) and “adverse selection” (caused by the failure to disclose information). Second, caucusing can help the mediator overcome a variety of negotiation problems, such as communication barriers, unrealistic expectations, emotional barriers, intraparty conflict, and fear of losing face. Third, caucusing provides a more private setting in which the mediator can develop a deeper and more personal understanding of the parties' needs and interests. Although the no-caucus model may be appropriate for certain types of mediation (particularly those cases in which the parties will have an ongoing relationship), some parties may prefer the efficiency that can be achieved with caucusing, even if that means sacrificing certain other values — such as greater understanding — or giving the mediator more information than the parties have, thus creating the risk of manipulation by the mediator. Moreover, the choice is not binary — numerous variations and hybrid formats can be useful, such as sessions in which the mediator meets with only the parties' lawyers or with only the parties. Choosing the best format for a mediation is more of an art than a science, and mediators should consider, with the parties, whether the parties' objectives would be best served using only joint sessions, extensive caucusing, or a combination of these approaches.