During 1976-1986, 3,336 athletes consulted the Turku Sports Medical Research Unit, 455 (14%) of these for Achilles tendon injuries. Achilles tendon problems were more frequent among joggers (66%), tennis players (32%) and runners (24%), which emphasizes the aetiological role of running. Achilles tendon complaints (n = 698) consisted of paratenonitis (including tendinopathies) (66%), insertional (23%) and myotendineal (8%) pain syndromes and total tendon ruptures (3%). The mean age of Achilles tendon injury patients was 26.1 years; among other sport injury patients it was 21.9 years (P less than 0.001). Surgery was performed in 24% of the subjects with paratenonitis and insertional pains. Different structural faults were found in 60% of the athletes with Achilles tendon overuse injuries. Forefoot varus correlated (r = P less than 0.001) with paratenonitis. A markedly limited total passive subtalar joint mobility and/or ankle joint dorsiflexion with knee extended was found in 6% of the conscripts, in 44% of the control athletes and in 58% and 70% of athletes with Achilles tendon paratenonitis and insertional pains, respectively. The range of motion of the ankle and subtalar joints was much lower in athletes than conscripts (P less than 0.001).