This 6-week, double-blind, randomised parallel group study was carried out to assess the efficacy and tolerability of 150 mg trazodone nocte and 30-60 mg mianserin nocte in the treatment of depression in general practice. Special emphasis was placed on the effect of treatment on psychomotor performance and sleep. A total of 39 suitable depressed patients were recruited into the study by one general practitioner. Nineteen of these were randomised to receive trazodone and 20 to receive 30 mg mianserin for the first 7 days and 60 mg for the remaining 5 weeks. Efficacy of the two therapies was assessed using the modified Hamilton depression rating scale scores and by the Investigator's judgement of both the global severity and improvement of the condition. For HAM-D scores no significant treatment differences were seen overall. There was, however, evidence that the trends in the scores over the 6-week trial period were different for the two therapies and that the scores changed significantly over this time. For current global severity and global improvement scores, there were no significant differences between treatments. The severity and improvement scores were found to change significantly over the 6 weeks of therapy in both of the two treatment groups. Psychomotor performance was assessed using the critical flicker fusion threshold test, the digit symbol substitution test and the choice reaction task.(ABSTRACT TRUNCATED AT 250 WORDS)