Pruritus is a common side effect after neuraxial administration of the opioids; particularly morphine sulfate. Ondansetron has been used to treat the pruritus in patients with cholestatic diseases or renal insufficiency, suggesting that pruritus may be mediated by serotonin. We administered ondansetron to four patients suffering from pruritus due to the perioperative administration of opioids. Pruritus disappeared within few minutes in three of these patients. Future studies are necessary to evaluate the efficacy of ondansetron for the treatment as well as the prevention of this opioid-induced effect.