The etiology underlying ruptures of the Achilles tendon is analyzed in 65 patients in a retrospective clinical study. A typical mechanism leading to a rupture of the tendon consists in an extraordinary tension force applied on a tendon in a state of active preload. A spontaneous rupture was observed in merely 3 cases. In 21 out of 65 patients risk factors such as hypercholesterolemia, hyperuricemia and arteriosclerosis were present. A systematic application of corticosteroids proved to be a decisive factor in the etiology of a tendon rupture. There was no correlation between the presence of associated risk factors and the degree of histological degeneration. During follow-up 3 re-ruptures and 6 ruptures of the contralateral tendon were registered. Our results lead to the conclusion that the etiology of the rupture of the Achilles tendon is based on a multifactorial disposition which includes the mechanism of injury, preexistent risk-factors as well as degenerative changes in the tendon structure.