The sample investigated consisted of two groups of emotionally labile healthy male subjects who were given either 100 mg/day of the antiepileptic drug carbamazepine (n = 16) or placebo (n = 16) for 8 days. Subjects were selected on the basis of their scores in the neuroticism scale of the Freiburg Personality Inventory (FPI-A: N score greater than or equal to 6). By means of an extensive test battery (ratings of emotional state, emotional reactivity tests, performance tests, physiological parameters) at day 1 and day 8 of ingestion the psychotropic effects of carbamazepine were evaluated as well as the differences in effects after single and repeated administration. Behavioral effects could be demonstrated for carbamazepine after single administration, but the differences found were rather small and limited to four parameters. After several days of administration carbamazepine revealed clear effects on psychological parameters. It is concluded that a drug like carbamazepine needs more than a single administration to be effective in psychological tests, in contrast to tranquilizing, sedating, neuroleptic and stimulating drugs. Carbamazepine has this characteristic common with antidepressant drugs. The experiment demonstrated that carbamazepine is a drug which under the chosen dose level conditions has a positive influence on subjective emotional states, e.g. reduction of deactivation and emotional tension (anxiousness).