1. Sleep disturbance is a prominent symptom of major depression. Despite specific treatment with antidepressants, there is a substantial number of patients who improve in depressed mood but remain sleep disturbed. 2. Polysomnographic sleep (PSG) data and self reported sleep measures were assessed at baseline and after one week in 18 patients (35-65 years) randomly assigned to treatment with either trimipramine alone 200 mg/d (group 1) or trimipramine (200 mg/d) and additional serial partial sleep deprivation in the second half of the night (3x/week) (group 2). 3. In group 1 no marked changes between baseline and after treatment were found. 4. In group 2 the PSG data showed a significant increase of slow wave sleep and a compensatory decrease in stage 1. Sleep continuity improved in terms of numbers of awakenings, sleep onset latency and total sleep time. These changes were in parallel with the subjective estimation of sleep in group 2. 5. There was no significant difference in the Hamilton rating scale scores neither at baseline nor after treatment. 6. These observed effects on sleep following additional serial PSD therapy seem to occur independent from the antidepressive effect.