Introduction and hypothesis: The objectives were to determine the reoperation rate of primary pelvic organ prolapse (POP) surgery, to describe the age distribution of the women at primary surgery for those undergoing a reoperation, and to describe the incidence of second and third reoperations. Methods: We carried out a population-based registry study of Danish women above the age of 18 years when undergoing primary surgery for POP during the period 1996–2000. Data were retrieved from the Danish National Patient Register. All women were followed until one of the following events occurred: reoperation for POP, death, emigration, or end of follow-up period. Reoperation was defined as “repeated surgery in same compartment”. The cumulative incidence rate of reoperation was divided into three compartments (anterior, apical, and posterior) and was calculated using Kaplan–Meier plots. Results: A total of 18,382 procedures were performed on 11,805 women. After 20 years’ follow-up, the cumulated incidence rate of reoperation for POP in the anterior, apical, and posterior compartments was 12.4%, 7.9%, and 12.1% respectively. The overall rate of reoperation was 11.5%. Of women aged between 18 and 49 years of age at primary surgery, 26.9% had a reoperation, whereas in women between 50 and 90+ years of age at primary surgery, only 10.1% had a reoperation. Conclusions: This large study with up to 20 years’ follow-up has found that reoperation for POP is modest, that the reoperation rate is lowest for the apical compartment, but highest in all three compartments during the first year after primary surgery. The reoperation rate peaks in the group of women who had their primary surgery before the menopause in all three compartments.