Twenty paid healthy volunteers took a placebo, 10 mg of mianserin and 25 mg of amitriptyline, t.i.d. for two weeks each, in a double-blind cross-over manner. There was one week's "wash-out" between the treatments. Several psychomotor tests were done on the first, 7th and 14th days of each period with either alcohol (0.5 g/kg) or a placebo drink. Co-ordinative and reactive skills and critical flicker frequency were affected by all the drug-drink combinations while attention was slightly impaired only after amitriptyline alone or mianserin together with alcohol. Drug actions and drug-alcohol interactions were most obvious on the first day but declined towards the end of the drug periods. After mianserin the skills were impaired on the first day only, but after amitriptyline up to the 7th day in most of the tests. Both drugs seemed to interact additively with alcohol. Impairment of flicker fusion by amitriptyline + alcohol remained constant over the whole 2-week period. Psychomotor effects of antidepressants have practical importance in the acute phase of treatment. Their concurrent use with alcohol must increase accident risk in traffic.