In patients with a chronic rupture or rerupture of the Achilles tendon, the recommended treatment is surgical. Various surgical techniques have been reported in the literature; however, the outcome is rarely evaluated with a sufficiently long follow-up, using appropriate end-points. The purpose of this study was to evaluate the subjective and objective outcome following a new surgical treatment for chronic rupture or rerupture of the Achilles tendon using augmentation with a free gastrocnemius aponeurosis flap. A total of 28 consecutive patients (22 male and 6 female) with a mean (SD) age of 46 (10.4) years were evaluated at a median (range) of 29 (12-117) months after surgery. The surgical technique involved making a single incision and then using a free gastrocnemius aponeurosis flap to cover the tendon gap after an end-to-end suture. The patients were evaluated using the Achilles tendon rupture score (ATRS) and a detailed questionnaire relating to symptoms, physical activity and satisfaction with treatment. The functional evaluation consisted of a validated test battery measuring different aspects of muscle/tendon function of the gastrocnemius/soleus and Achilles tendon complex. The median (range) ATRS was 83 (24-100). There were no reruptures. In terms of surgical complications, there was one deep infection, three wound closure complications and deep venous thrombosis in two patients. All but one patient returned to work within 6 months of surgery. Sixteen (57%) patients were satisfied with the treatment. There was a significant decrease in the level of physical activity after the injury compared with before the injury (p = 0.004). Of the 25 patients who participated in recreational sports prior to injury, 13 (52%) returned to the same activity level after treatment. In terms of jump performance, no significant differences were found between the healthy and injured sides. There was, however, a significant decrease in strength, in terms of both concentric and eccentric-concentric toe raises and the toe-raise test for endurance compared with the healthy side. The use of a free gastrocnemius aponeurosis flap to treat chronic ruptures and reruptures of the Achilles tendon rendered a good overall subjective and objective outcome in the majority of patients. The use of a single incision in combination with a free flap augmentation produced favourable results.