OBJECTIVE Premenstrual dysphoric disorder is a menstrually related disorder that intermittently causes disabling emotional, behavioral, and physical symptoms. The goal of the current study was to evaluate the efficacy and tolerability of sertraline for premenstrual dysphoric disorder when treatment was limited to the luteal phase. METHODS Two hundred eighty-one women who met Diagnostic and Statistical Manual of Mental Disorders (4th edition) criteria for premenstrual dysphoric disorder and who completed two prospective screening cycles and one single-blind placebo cycle were randomized to three cycles of double-blind, luteal phase treatment with either a placebo or sertraline in a flexible daily dose of 50-100 mg. Outcome measures included the Daily Record of Severity of Problems and the Clinical Global Impression Severity and Improvement scales. RESULTS Luteal phase treatment with sertraline was significantly superior to the placebo, as demonstrated by end- point analysis of Clinical Global Impression Improvement scale scores (sertraline, 2.3 +/- 1.1, versus placebo, 2.7 +/- 1.1; P <.001), and cycle 3 Daily Record of Severity of Problems change scores (sertraline, 27.6 +/- 26.8, versus placebo, 17.6 +/- 23.3; P <.002). A significant difference was also noted in responder rates in favor of sertraline (50%) versus placebo (26%, P <.001) by cycle 1 (with responder defined as a Clinical Global Impression Improvement scale score of 1 or 2). Quality of life and functioning outcomes were also significantly improved. Intermittent luteal administration of sertraline was well tolerated, with only approximately 8% of patients on sertraline and less than 1% on placebo discontinuing because of adverse events. CONCLUSIONS Sertraline was significantly more effective than a placebo and was well tolerated as a treatment for premenstrual dysphoric disorder when administered intermittently during the luteal phase of the menstrual cycle.