A polysomnographic study was conducted on 10 outpatients with major depression at baseline and during 4 to 8 weeks of open-trial treatment with nefazodone (400 to 600 mg/day). All 10 patients were treatment responders as evidenced by at least 50% reduction from baseline scores on the Hamilton Depression Rating Scale. Nefazodone was associated with significantly decreased wake and movement time and increased minutes and percentage of stage 2 sleep at the expense of light stage 1 sleep. Nefazodone did not increase rapid-eye-movement (REM) latency and it did not suppress REM sleep. In fact, a trend toward increased REM in the second REM period was observed, although decreased REM in the third REM period was also noted. In summary, nefazodone, an effective antidepressant, decreases arousals and wakefulness during sleep and reduces light non-REM sleep. This agent does not appear to suppress REM sleep or prolong REM latency in patients who respond to treatment.