90 patients scheduled for total knee arthroplasty under spinal anesthesia and intrathecal morphine were randomized to antiemesis with either ramosetron or ondansetron. Patients were assessed for the incidence of nausea and vomiting, and severity of nausea, over the first 48 hours postoperatively. Results demonstrated a significantly lower incidence of nausea in the ramosetron group compared to the ondansetron group at 6 hours and from 12-24 hours postoperatively. Additionally, the incidence of vomiting was significantly lower in the ramosetron group compared to the ondansetron group from 18-24 hours postoperatively.