Ethanol (1.5 g/kg i.v.) was found to decrease spontaneous complex spike (CS) activity in cerebellar Purkinje cells in urethane anaesthetized rats while not changing the threshold required to evoke a CS by juxtafastigial stimulation. Thus ethanol does not decrease CS activity by an action at the climbing fibre-Purkinje cell synapse. Tremor induced by harmaline (5 mg/kg i.v.) in unanaesthetized animals was markedly antagonized by ethanol (0.5-2.0 g/kg i.v.) in all animals tested. However, in nine urethane-anaesthetized animals, ethanol markedly reversed the effects of harmaline on Purkinje cells in only two cases and partially reversed the effects in another four cells. Thus, the depressant effects of ethanol on the inferior olive is not total responsible for the blockade of the harmaline tremor bur would account for the decrease in spontaneous CS activity.