Postoperative nausea and vomiting (PONV) with morphine therapy develops in more than 60% of patients after surgery, markedly reducing patient QOL. The prophylactic eŠect of several antiemetics has already been studied, but evaluations, and even those using the same drug, are not uniform. The present research involved a meta-analysis of randomized controlled trials on prophylactic drug therapy for PONV in patients receiving morphine for the treatment of postoperative pain. The e‹cacy of the prophylactic administration of the drugs was examined.As a result, meta-analysis ofˆve drugs was possible and the evidence of e‹cacy was shown for three drugs ranked in order of an increasing odds ratio (OR) and conˆdence interval (CI): dexamethasone (OR: 0.23, 95% CI: 0.15-0.35, p< 0.00001), droperidol (OR: 0.27, 95% CI: 0.21-0.34, p<0.00001), and metoclopramide (OR: 0.48, 95% CI: 0.30-0.75, p<0.001). These results suggest that the three drugs are eŠective in prophylactic treatment for PONV. Of them, dexamethasone used as a prophylactic drug for PONV provided the best results. Dexamethasone was shown to reduce the incidence of PONV from 66-80% to 16-50% with a dose of 1.25 to 10 mg and to be suitable as aˆrst drug of choice.