We report six cases of rapid mood cycling induced by antidepressant treatment. The key to effective treatment involved the recognition of the pattern of apparent remission, relapse, antidepressant and/or stimulant adjustment, remission, relapse,etc. Hypomanic episodes were frequently mild and could be mistaken for remission. The destabilizing effects of antidepressant drugs were not corrected by the addition of mood stabilizers, necessitating the withdrawal of the antidepressant agent. All but one case responded to such withdrawal. Two cases required the addition of high-dose L-thyroxine for stabilization. Implications for an effective treatment protocol are discussed.