We studied 79 cases of surgically treated Achilles tendon overuse injuries in 66 patients. Fifty-three (80%) of these patients were competitive or serious recreational runners operated on between 1978 and 1991. There were 49 men and 17 women with a mean age of 33 years (range, 17 to 59). The cases were divided into surgical subgroups based on their site of primary symptoms and abnormalities: paratenonitis (23), tendinosis (partial rupture or degeneration) (15), retrocalcaneal bursitis (24), insertional tendinitis (7), and combined abnormalities (10). Followup included a comprehensive patient questionnaire and office examination. There were 79% satisfactory (51% excellent, 28% good) and 21% unsatisfactory (17% fair, 4% poor) results. The percentages of satisfactory results in the paratenonitis group (87%) were best and those in the tendinosis group were the worst (67%). Satisfactory results were obtained in 75% of the patients with retrocalcaneal bursitis and 86% with insertional tendinitis. Seven of the 45 cases with longer than 5-year followup with initially satisfactory results deteriorated with time and required reoperation (16%). Of these, 4 were in the tendinosis group, 2 had retrocalcaneal bursitis, and 1 had paratenonitis. One of the 34 patients followed less than 5 years required reoperation.