In a placebo controlled double-blind cross-over study, the cardiovascular and antidepressant effects of three weeks' treatment with mianserin (30-80 mg daily) and trazodone (150-400 mg daily) were studied in depressed patients who had co-existant cardiac disease. In 14 of the 16 patients, no haemodynamic deterioration occurred with either drug. Two patients withdrew from the study. One with coronary artery disease, whose concomitant medication included a calcium-antagonist and a beta-adrenoceptor blocker and who developed severe postural hypotension after his first dose of trazodone while the other had an increased frequency of transient cerebral ischaemic attacks with both mianserin and trazodone, but not with placebo. Mianserin and trazodone are comparable for both antidepressant efficacy and paucity of cardiovascular effects. Although unwanted effects were generally mild, the incidence of dizziness was greater in those patients receiving trazodone. Caution is advised, however, when prescribing either drug to patients with transient cerebral ischaemic attacks or those with coronary artery disease receiving medication.