This study investigated the effects of open-label fluoxetine (20 mg/d) on the polysomnogram (PSG) in depressed outpatients (n = 58) who were treated for 5 weeks, after which dose escalation was available (< or = 40 mg/d), based on clinical judgment. Thirty-six patients completed all 10 weeks of acute phase treatment and responded (HRS-D < or = 10). PSG assessments were conducted and subjective sleep evaluations were gathered at baseline and at weeks 1, 5, and 10. Of the 36 subjects who completed the acute phase, 17 were reevaluated after 30 weeks on continuation phase treatment and 13 after approximately 7 weeks (range 6-8 weeks) following medication discontinuation. Acute phase treatment in responders was associated with significant increases in REM latency, Stage 1 sleep, and REM density, as well as significant decreases in sleep efficiency, total REM sleep, and Stage 2 sleep. Conversely, subjective measures of sleep indicated a steady improvement during acute phase treatment. After fluoxetine was discontinued, total REM sleep and sleep efficiency were found to be increased as compared to baseline.