The epidemiology of Achilles tendon ruptures was examined during the 13-year period 1984-1996 in a Danish county. Five hospitals, serving a population of 220,000 cooperated. There were 718 ruptures, 544 men (75.8%) and 174 women (24.2%). The male to female ratio was 3:1. The average age was 42.1 years (3-82) and 62% were between 30-49 years. 74.2% of the ruptures were sport-related and 89% of these occurred in ball and racket games. The annual incidence of achilles tendon ruptures increased from 18.2/10(5) inhabitants in 1984 to 37.3/10(5) in 1996. The peak incidence in sport-related ruptures occurred in the age group 30-49 years, but ruptures not related to sport occurred in older patients with a peak incidence in those 50-59 years.