Approximately 10% of women are severely affected by premenstrual syndrome (PMS) during their reproductive years. Several biological theories of causation have been proposed and each has provoked treatment attempts through medication to little sustained effect. As many of the reported complaints are psychological, a new treatment approach was considered using cognitive-behavioral therapy. A preliminary study which combined cognitive-behavioral therapy with drug treatment produced considerable symptom reduction. The present study examined the efficacy of cognitive-behavioral therapy alone in direct comparison with hormone treatment. Relaxation instructions were provided to a control group. Initial rapid responses to drug treatment and relaxation diminishes after 2 months, together with marked attrition in the control group. Significant positive benefits from cognitive-behavioral therapy were achieved after the first treatment month that continued throughout and were maintained at follow-up 3 months later. Implications for future management are discussed.