A pharmacokinetic analysis of a new antidepressant drug, mianserin (ORG GB-94), was undertaken in 4 male volunteers, each of whom received 15 mg mianserin on two occasions. Plasma levels peak at 2 h with a median level of 11.0 ng/ml, a median beta-phase half-life of 10.0 h, and a median apparent volume of distribution of 3.3 X 10(3) 1. EEG profile analysis shows mianserin to increase frequencies below 6 Hz, decrease those from 7.5 to 15 Hz, and increase frequencies above 18 Hz, a pattern similar to amitriptyline. Peak EEG effects range from 2 to 5 h with a pattern of measured changes that parallels plasma levels with varying latency. Decreases in vigilance measures and in critical flicker-fusion frequency show a similar time course. Mianserin is a putative thymoleptic on EEG profile analysis with high cerebral penetrance.