Procedure After informed consent, surgical patients scheduled for outpatient abdominal surgery at the Central Arkansas Veterans Healthcare System (CAVHS) who are at high risk for developing PONV following their procedure will be randomized to receive either the study drug ( preoperative oral dronabinol-5 mg) or standard therapy ( 4 mg ondansetron intravenously at the end of surgery). The outcome measures will be the presence or absence of PONV, the severity and number of such episodes, the event count of rescue antiemetic use and patient satisfaction. All data will be recorded by personnel who are blinded to the drug regimen.