Does the evidence now available support the concept of premenstrual dysphoric disorder (PMDD) as a distinct clinical disorder such that the relative safety and efficacy of potential treatment can be evaluated? In a roundtable discussion of this question, a wealth of information was reviewed by a panel of experts. The key characteristics of PMDD, with clear onset and offset of symptoms closely linked to the menstrual cycle and the prominence of symptoms of anger, irritability, and internal tension, were contrasted with those of known mood and anxiety disorders. PMDD displays a distinct clinical picture that, in the absence of treatment, is remarkably stable from cycle to cycle and over time. Effective treatment of PMDD can be accomplished with serotinergic agents. At least 60% of patients respond to selective serotonin reuptake inhibitors (SSRIs). In comparison with other disorders, PMDD symptoms respond to low doses of SSRIs and to intermittent dosing. Normal functioning of the hypothalamic-pituitary-adrenal (HPA) axis, biologic characteristics generally related to the serotonin system, and a genetic component unrelated to major depression are further features of PMDD that separate it from other affective (mood) disorders. Based on this evidence, the consensus of the group was that PMDD is a distinct clinical entity. Potential treatments for this disorder can now be evaluated on this basis to meet the clear need for effective therapy.