• Five women with primary, major, bipolar affective disorder, characterized by rapid mood cycles and nonresponsiveness to conventional drug treatments, including lithium carbonate, were given low doses (2.5 to 10.0 mg/24 hr) of clorgyline, a selective inhibitor of monoamine oxidase type A. In four patients, clorgyline, alone or in combination with lithium carbonate, prolonged the duration and lessened the severity of mood cycles. One patient experienced prolonged manias while receiving clorgyline therapy. Clorgyline-induced remissions have lasted from three to more than 12 months.