Breasts are known to show cyclic changes in accordance with the menstrual cycle, and speculations have been made regarding the ideal timing of breast surgery in this extent, but the clinical evidence to support global acceptance and application is lacking. This study was designed to establish the relationship of intraoperative bleeding and postoperative drainage with the menstrual period of 35 reduction mammaplasty patients. The results indicate that both perioperative blood loss and postoperative drainage were significantly reduced when breast reduction is performed during the periovulatory phase compared with the perimenstrual phase. The authors strongly recommend the interval between days 8 and 20 of the menstrual cycle as a more convenient period to perform breast reduction. Drains may be avoided during this period, but they are preferred if the surgery is done during the perimenstrual phase.