The potential for preoperative IV rehydration to reduce postoperative nausea and vomiting (PONV) and pain in patients undergoing ambulatory surgery remains unclear, with conflicting results reported. We sought to determine whether preoperative IV rehydration with a balanced salt solution would decrease the incidence of PONV in patients at increased risk for these symptoms. Eighty ASA grade I-III patients presenting for gynecologic laparoscopy were randomized to receive large (2 mL/kg per hour fasting) or small (3 mL/kg) volume infusions of compound sodium lactate solution over 20 min preoperatively. A standardized balanced anesthetic was used. The incidence and severity of PONV and pain, and need for supplemental antiemetic and analgesic therapy, were assessed by a blinded investigator at 0.5, 1, and 4 h postoperatively, and on the first and third postoperative days. The incidence (control 87% versus large volume 59%) and severity of PONV were significantly reduced in the large volume infusion group at all time intervals. The large volume infusion group also had decreased postoperative pain scores and required less supplemental analgesia. Preoperative correction of intravascular volume deficits effectively reduces PONV and postoperative pain in high risk patients presenting for ambulatory surgery. We recommend the preoperative administration of 2 mL/kg of compound sodium lactate for every hour of fasting to patients with an increased PONV risk presenting for ambulatory surgery.