Trazodone (150 mg to 400 mg) was administered to six depressed patients with significant sleep disturbances in an 8-week single-blind study design. Patients were evaluated psychologically by means of the Hamilton Rating Scales for Anxiety and Depression. Polysomnographic monitoring in the sleep laboratory was conducted at each of the time points corresponding to the psychiatric evaluations. Five of the six subjects completed treatment. Patients showed a significant improvement in symptoms of depression and in their polysomnographic-determined sleep architecture. There was a 44% improvement in persistent sleep latency, decreasing from a mean +/- SD of 51.0 +/- 59.3 minutes at baseline to 28.5 +/- 24.2 minutes after 5 weeks of active treatment. Total sleep time improved 14% from 387.1 +/- 59.2 minutes at baseline to 441.3 +/- 23.7 minutes after 5 weeks. Stage IV sleep more than doubled with an increase of 153% from 1.9 +/- 3.0% at baseline to a more normal 4.8 +/- 5.5%. There was no change in percentage of rapid eye movement (REM); however, REM latency increased 28% from a mean of 74.6 +/- 35.9 minutes at baseline to a mean of 95.6 +/- 28.8 minutes. Sleep efficiency improved from 80.6 +/- 12.3%, considered clinically significant insomnia, to 91.9 +/- 4.9%, which is well within normal sleep patterns.