Bupropion hydrochloride is a phenylaminoketone antidepressant whose clinical pharmacology is poorly understood. Part of bupropion's action may be attributed to inhibition of dopamine reuptake that may induce organic mental disorders in certain susceptible patients. We report three cases of organic mental disorders in patients receiving bupropion hydrochloride for treatment of the depressed phase of their bipolar-type mood instability. The organic mental disorders that occurred in these patients were characterized largely by visual disturbances--visual hallucinations and visual illusions--although one patient also experienced auditory hallucinations. The patients' use of concomitant medications and potential drug interactions are carefully evaluated and the literature on bupropion's ability to induce organic mental disorders is reviewed. We suggest a number of possible mediating mechanisms for these syndromes including dose-related dopaminergic augmentation, accumulation of toxic metabolites, predisposition to psychosis, and drug interactions.