Groin hernia repair is a commonly performed surgical procedure in the western world but large-scaled epidemiologic data are sparse. Large-scale data on the occurrence of groin hernia repair may provide further understanding to the pathophysiology of groin hernia development. This study was undertaken to investigate the age and gender dependent prevalence of groin hernia repair.In a nationwide register-based study, using data from the Civil Registration System covering all Danish citizens, we established a population-based cohort of all people living in Denmark on December 31(st), 2010. Within this population all groin hernia repairs during the past 5 years were identified using data from the ICD 10(th) edition in the Danish National Hospital Register.The study population covered n = 5,639,885 persons. During the five years study period 46,717 groin hernia repairs were performed (88.6% males, 11.4% females). Inguinal hernias comprised 97% of groin hernia repairs (90.2% males, 9.8% females) and femoral hernias 3% of groin hernia repairs (29.8% males, 70.2% females). Patients between 0-5 years and 75-80 years constituted the two dominant groups for inguinal hernia repair. In contrast, the age-specific prevalence of femoral hernia repair increased steadily throughout life peaking at age 80-90 years in both men and women.The age distribution of inguinal hernia repair is bimodal peaking at early childhood and old age, whereas the prevalence of femoral hernia repair increased steadily throughout life. This information can be used to formulate new hypotheses regarding disease etiology with regard to age and gender specifications.