OBJECTIVES: Iatrogenic chronic pain is increasingly recognized as a major adverse outcome after inguinal hernia repair. In order to assess chronic post-herniorrhaphy pain, we developed the 18-item Inguinal Pain Questionnaire (IPQ). The aim of the present study was to test its validity and reliability and explore the prevalence of long term pain as determined by the questionnaire in a sample from the population-based Swedish Hernia Register. METHODS: Validity was tested in 100 patients who received the IPQ and the Brief Pain Inventory (BPI) 1 and 4 weeks after surgery (Group A). The reliability was tested in 100 patients who received the IPQ on two occasions one month apart 3 years after operation (Group B). From the Swedish Hernia Register 2853 operated 2000 were requested to fill in IPQ by mail. RESULTS: As an indication of construct validity, a significant (p<0.001) decrease in IPQ-rated pain intensity was observed in the first 4 weeks after surgery. Significant (p<0.05) correlations with corresponding BPI pain intensity items corroborated the criterion validity. The rate of logical incoherence did not exceed 5.5% for any item. Kappa values in the test-retest one month apart in group B were higher than 0.5 for all but three items, indicating acceptable reliability. Cronbachs alpha was 0.83 for questions on pain intensity and 0.51 for interference with daily activities. After two reminders, 2456 patients (86%), in the sample from the Hernia Register had responded to the questionnaire. In response to a question about “worst perceived pain last week”, 758 patients (31%) reported pain to some extent. In 144 cases (6%) the pain interfered with daily activities. CONCLUSION: The validity and reliability is sufficient to make IPQ a useful instrument in the routine assessment of post-herniorrhaphy pain. Disabling pain was found to be a widespread problem 3 years after surgery.