Postoperative nausea and vomiting is a major cause of postoperative morbidity. It can lead to increased recovery time, delaying patient discharge and an increase in hospital costs. Past studies have shown that postoperative nausea and vomiting is more frequent in women than men, appears to elevate around the time of menarche and is reduced around the time of menopause. This retrospective review of a one-year experience of laparoscopic tubal ligation at our institute examined the effect of menstrual cycle on postoperative nausea and vomiting. The anaesthetic and surgical techniques were consistent for all patients. Patient data included age, weight, last day of menstrual cycle, the length of anaesthetic, the dose of inhalational agent, the dose of narcotic, emesis on emergence and whether or not droperidol was used. Of the 235 patients in the study, the incidence of nausea and vomiting was 28%. One hundred fifty-eight had had no preoperative antiemetic and 77 had received droperidol. These two groups were analyzed separately. The incidence in the group not receiving droperidol was 33.5% and in the droperidol group, 16.9% (P < 0.01). The incidence of nausea and vomiting was higher on the first eight menstrual days (51.6 vs 21.6, P < 0.001), was highest on day five of the menstrual cycle and lowest on days 18, 19, and 20 where there was no nausea and vomiting. Droperidol reduced the incidence of postoperative nausea and vomiting but the variation in postoperative nausea and vomiting during the cycle persisted. These data suggest that the scheduling of laparoscopy according to menstrual cycle may be more effective than droperidol alone in reducing postoperative nausea and vomiting. The relative risk of nausea and vomiting is four times greater during menses.