We have reviewed 106 patients after treatment for spontaneous rupture of the calcaneal tendon, and assessed the clinical results including the power of plantarflexion. In patients treated within 48 hours of injury the result was very similar in conservatively and in operatively treated patients. The incidence of major complications was higher after operation (17%) than in those treated conservatively (4%). Patients who were treated more than one week after injury, however, had an inferior result with respect to power of plantarflexion after conservative management. It is therefore recommended that calcaneal tendon rupture is treated conservatively with a plaster in full equinus when it is diagnosed within 48 hours of injury, and by operation when diagnosis has been delayed for more than one week.