BACKGROUND Postoperative pain and postoperative vomiting (POV) are both sources of distress in the postoperative period. Patient-controlled epidural analgesia (PCEA) is used in patients undergoing lower extremity surgery to improve postoperative quality but is accompanied by a certain incidence of vomiting. We wanted to determine the risk factors of POV in patients using PCEA with the aim of improving the quality of the postoperative period. METHODS We conducted a retrospective study to analyze the risk factors among patients using PCEA after lower-limb surgery under regional anesthesia. A total of 195 patients (91 males, 104 females) were enrolled. They were categorized into 2 groups: vomiting and non-vomiting. We found that female gender predominated in the vomiting group. Hence, we analyzed the female subgroup in order to find the risk factors of vomiting in the female PCEA population. RESULTS Female gender was the most significant factor related to vomiting (crude OR, 11.55; 95% CI, 4.88-27.33). From analysis of the female subgroup, puncture site (OR, 4.07; 95% CI, 1.41-11.79), catheter length in the epidural space (OR, 0.28; 95% CI, 0.16-0.50) and patient's height (OR, 1.07; 95% CI, 1.00-1.14) were also factors for vomiting, i.e. higher epidural catheter puncture site, shorter length in the epidural space, and greater height caused a higher incidence of POV. CONCLUSION The most important risk factor for POV in patients using PCEA was female gender. Among the female subgroup, the risk factors for POV included higher epidural catheter puncture site, shorter length in the epidural space and greater body height.