The effects of fencamfamine (25 and 50 mg po) were studied on acute psychophysiological and psychomotor performance in six healthy male volunteers. Stimulant effects, such as greater increases of critical flicker-fusion threshold, heart rate, blood pressure and stimulation assessed by self-rating, were more pronounced with the higher dose of fencamfamine. Paradoxical sedative effects were obtained with the 25 mg dose. Fencamfamine should not be considered only as an energizing agent, but also as an agent having a psychostimulant profile of effects.