We determined the incidence of a total Achilles tendon rupture in the city of Oulu and changes over the 16-year period 1979-1994. During this time, 110 ruptures occurred. The incidence increased from 2 ruptures/10(5) inhabitants in 1979-1986 to 12 in 1987-1994, with a mean of 7. The peak annual incidence, 18, was recorded in 1994. The incidence was highest in the age group 30-39 years. Male dominance was 5.5:1, and 81% of the ruptures were related to sports, with 88% occurring in ball games. The mean age was significantly lower for the sports injuries.