BACKGOUND: This study was designed to examine the effects of female hormones and the menstrual cycle on postoperative pain. METHODS: Ninety women who underwent gynecologic surgery involving a lower abdominal incision were asked for information regarding their menstrual cycles, and blood samples were obtained to determine the progesterone and estrogen levels of the patients at the time of surgery. Patient controlled analgesia was applied to control postoperative pain and an estimate of the consumption of analgesic drugs by the patients was made. Analgesic consumption and pain scores were recorded at 2, 24, and 48 hours after operation. RESULTS: There was no relationship observed between the concentration of progesterone and estrogen and the consumption of analgesic drugs. However, patients that were in the luteal phase at the time of surgery consumed a significantly lower amount of analgesic drugs during the 2-24 hours following surgery than patients that were in the follicular phase (19.4 +/- 6.5 ml vs 24.6 +/- 11.0 ml, P < 0.05), Theree was, no significant difference in pain scores between two menstrual phases. CONCLUSIONS: This study demonstrates that there is less postoperative pain experienced by patients that are in the luteal phase of their menstrual cycle at the time of surgery than in patients that were in the follicular phase of their menstrual cycle, however, the results of this study did not reveal a relationship between the blood concentration of female hormones and postoperative pain.