Opioid-based intravenous patient-controlled analgesia (IV PCA) is popular method of postoperative pain control, but many patients suffer from IV PCA-related postoperative nausea and vomiting (PONV). In this retrospective observational study, we have determined independent predictors of IV PCA-related PONV and predictive values of the Apfel's simplified risk score in pursuance of identifying high-risk patients. We analyzed 7000 patients who received IV PCA with background infusion after elective surgery. Patients who maintained IV PCA for a postoperative period of 48 hr (completion group, n=6128) were compared with those who have discontinued IV PCA within 48 hr of surgery due to intractable PONV (cessation group, n=872). Patients, anesthetics, and surgical factors known for predicting PONV were evaluated by logistic regression analysis to identify independent predictors of IV PCA related intractable PONV. In a stepwise multivariate analysis, weight, background infusion dose of fentanyl, addition of ketolorac to PCA, duration of anesthesia, general anesthesia, head and neck surgery, and Apfel's simplified risk score were revealed as independent risk factors for intractable PONV followed by the cessation of IV PCA. In addition, Apfel's simplified risk score, which demonstrated the highest odds ratio among the predictors, was strongly correlated with the cessation rate of IV PCA. Multimodal prophylactic antiemetic strategies and dose reduction of opioids may be considered as strategies for the prevention of PONV with the use of IV PCA, especially in patients with high Apfel's simplified risk scores.