1 Bupropion, a novel antidepressant, has been compared with nomifensine and dexamphetamine in a controlled double blind trial in 12 healthy volunteers. 2 Signals detected in an auditory vigilance test were increased by dexamphetamine 5 and 10 mg when compared with lactose dummy, but unaffected by bupropion 100 and 200 mg and nomifensine 100 mg. Auditory reaction time was decreased by dexamphetamine but unaffected by bupropion and nomifensine. 3 Heart rate was increased after all active treatments but the largest rise followed dexamphetamine 10 mg which differed from both lactose dummy and all other active treatments. Systolic blood pressure was higher after dexamphetamine 10 mg than all other treatments, none of which differed from lactose. No changes occurred in diastolic blood pressure. Pupil size increased after dexamphetamine 10 mg but no changes followed other treatments. 4 Visual analogue scales showed that subjects were more alert, attentive, proficient, excited, interested and elated after dexamphetamine but no changes followed bupropion or nomifensine. Subjects were able to recognise that they had received an active drug only after dexamphetamine 10 mg.5 Increased activity was seen in the 7.5-13.5 Hz and 13.5-26 Hz frequency bands of the electroencephalogram after dexamphetamine 10 mg but not after bupropion or nomifensine. 6 These findings in man suggest that neither of these two, non-sedative antidepressants possess amphetamine-like stimulant activity, and are discussed in relation to the animal pharmacology of the drugs.