BACKGROUND:: In this study, we investigated whether melatonin administration could improve postoperative subjective sleep quality and reduce discomfort. METHODS:: One hundred twenty-one patients scheduled for elective ambulatory laparoscopic cholecystectomy were randomized to oral 5 mg melatonin (n = 60) or placebo (n = 61) for 3 nights after surgery. Subjective sleep quality, sleep duration, sleep timing, and subjective discomfort (fatigue, general well-being, and pain) were measured. RESULTS:: Sleep latency was significantly reduced in the melatonin group (mean [sd] 14 min ) compared with placebo (28 min ) on the first postoperative night (P = 0.015). The rest of the measured outcome variables did not differ between groups. CONCLUSIONS:: Melatonin did not improve subjective sleep quality or discomfort compared with placebo after laparoscopic cholecystectomy.