Sixteen young male volunteers received single doses of moclobemide 200 mg, moclobemide 400 mg, amitriptyline 50 mg and placebo in a double-blind crossover study. Subjects then completed a test battery which is sensitive to the effects of psychoactive drugs at 1, 2, and 4 h post-dose. The test battery included tasks of choice reaction time, tracking, critical flicker fusion threshold and memory scanning. Subjective feelings were assessed using the Leeds sleep evaluation questionnaire (LSEQ) and line analogue rating scales (LARS). The results show that the positive internal control (amitriptyline) has a sedative effect in that it increased critical flicker fusion threshold, reaction time and tracking error. Moclobemide 400 mg increased reaction time in the tracking task but neither dose of moclobemide impaired psychomotor performance or cognitive ability in any of the other tests.