BACKGROUND Radical retropubic prostatectomy is a potentially curative treatment for localized prostate cancer. This study aimed to examine the incidence of developing inguinal hernia after radical retropubic prostatectomy and its possible factors. METHODS From November 1990 to April 2002, there were 222 patients in Kaohsiung Veterans General Hospital who underwent radical retropubic prostatectomy and pelvic lymph node dissection for localized prostate cancer. Another 200 patients with prostate cancer who did not receive surgical intervention were enrolled as the control group. The medical charts were reviewed with an emphasis on the possible mechanisms causing inguinal hernia. RESULTS The period of follow-up ranged from 2 to 137 months, with a median of 54 months. There were a total of 15 (6.7%) patients who developed inguinal hernia after radical retropubic prostatectomy and pelvic lymph node dissection in our hospital. Post-prostatectomy anastomotic stricture was noted in 7 (46%) patients. Ten patients (67%) developed indirect type inguinal hernia. Only 4 (2%) inguinal hernias were found in the control group. CONCLUSIONS The incidence of inguinal hernia among patients undergoing radical retropubic prostatectomy and pelvic lymph node dissection was higher than that among patients without operation. Post-operative anastomotic stricture was the most important predisposing factor in the current study.