Three bipolar manic-depressive patients are described who, after responding to bupropion treatment for an acute depressive relapse, were maintained on the drug alone for a 1-year period, without recurrences of mania or depression. Discontinuation of medication was followed within 8 weeks by a manic or depressive recurrence in all three cases. Data are presented to suggest that bupropion probably exerted a prophylactic effect in preventing acute affective recurrences in these cases. This drug merits investigational attention as an alternative approach to current maintenance chemotherapy of recurrent affective disorder.