The chemistry, pharmacokinetics, pharmacology, clinical efficacy, adverse effects, and dosage of bupropion hydrochloride, an aminoketone antidepressant, are reviewed. Bupropion is rapidly absorbed after oral administration and demonstrates a first-order absorptive phase. Bupropion has biphasic elimination with a redistribution half-life of about one hour and an elimination half-life of 11-14 hours. Bupropion is widely distributed to tissues and extensively metabolized by oxidation and reduction to at least six metabolites, some of which may be active. Bupropion does not inhibit monoamine oxidase, exerts no effect on serotonin uptake, and minimally alters the reuptake of norepinephrine at presynaptic sites. It does not appear to exert action leading to postsynaptic beta-adrenergic down-regulation, and it has minimal inhibitory effects on presynaptic dopamine uptake. Bupropion has been shown to be as effective as tricyclic antidepressants (TCAs), with particularly well-documented efficacy in depressed patients with manic-depressive illness in several controlled clinical trials. Bupropion causes fewer anticholinergic, orthostatic, and cardiac conductive side effects than TCAs. Elderly patients may be given full adult doses of bupropion, and preliminary experience with overdoses suggests that it is a relatively safe drug for patients with suicidal ideation. The usual adult daily dose of bupropion hydrochloride is 300-750 mg, depending on the severity of the depression. In all cases, bupropion should be given in three doses daily. Bupropion is an effective antidepressant with a good side-effect profile; it is a useful alternative for patients unresponsive to or intolerant of therapeutic doses of TCAs.