Postoperative nausea and vomiting were compared in 68 women with regular menstrual periods undergoing gynaecological laparoscopy. The patients were divided into four group on the basis of the phase of the menstrual cycle as follows: premenstrum-menstrum (pre + menstrum) (Pd 25-6), early follicular phase (Pd 8-12), ovulatory phase (Pd 13-15) and luteal phase (Pd 20-24). The overall incidence of nausea and vomiting was 46%. Statistically significant differences in the incidence of nausea and retching were found among the groups by regression analysis. The incidence of nausea and vomiting was highest in women undergoing laparoscopy during the luteal phase (77%), which was greater than during the follicular phase (32%) or during pre + menstruation (18%). The need for antimetic was highest in women undergoing laparoscopy during the luteal phase (69%) and this was different from the follicular (18%, P less than 0.01) and pre + menstrum (19%, P less than 0.01) phases. It is concluded that the highest incidence of postoperative nausea and vomiting after gynaecological laparoscopy occurs during the luteal phase.