The interaction of mianserin with ethanol in central nervous system (CNS) was investigated. Mianserin was administered at a single dose of 5 or 20 mgkg(-1) i.p. or as daily injections in a dose of 2.5 mgkg(-1) given for 14 days. The influence of mianserin on acute ethanol toxicity (LD(50)), on ED(50) of ethanol in rota-rod test, on the duration of ethanol sleeping time as well as on spontaneous locomotor activity and ethanol-induced hypothermia was investigated. Moreover, the influence of mianserin administered in a dose of 10 mgkg(-1) i.p. on post-ethanol changes in the bioelectric brain activity (EEG) recordings in rabbits was also investigated. The electrodes were implanted into midbrain reticular formation (MRF), dorsal hippocampus (Hp) and frontal cortex (C). Mianserin administered as a single dose of 5 mgkg(-1) was found to decrease LD(50) of ethanol and its ED(50) in rota-rod test. Mianserin administered as a single dose of 5 or 20 mgkg(-1) prolongs ethanol sleeping time in mice but given daily for 14 days has no influence on this time. Mianserin-induced hypothermia was observed after administration of single dose as well as increase of ethanol-induced hypothermia after administration of higher dose (20 mgkg(-1)). Mianserin administered daily for 14 days had no influence on post-ethanol changes in body temperature. Single dose of mianserin 20 mgkg(-1) decreases locomotor activity in mice while repeated administration has no influence on locomotor activity. In contrast, both single dose and repeated administration of mianserin prevents increased locomotor activity of animals observed after ethanol (2.5 mgkg(-1)). Mianserin administered to rabbits (10 mgkg(-1)) induces increase of share of low frequency 0.5-4 cps and decrease of share of frequencies 4-7 and 7-10 cps in EEG recordings from MRF and Hp. The recordings from frontal cortex show increase of share of frequencies 10-13 cps. Ethanol increases the share of low frequencies in EEG recordings and decreases the share of fast frequencies. Mianserin increases its influence on fast frequencies.