In this prospective study,73 patients (with an average age of 36 years) were examined by ultrasound to compare the results of open Achilles tendon surgery, percutaneous tendon adaptation, and conservative treatment. Once the accident reports had been collected, all of the patients presented themselves at the Sportklinik Stuttgart at intervals of 4, 8, 12, 26 weeks, and approx. 2.5 years after the accident. During the course of these examinations, the thickness and structure of the tendon was quantified via ultrasound and the quality by clinical examination. The results of the ultrasonic quantification of the healing process appeared to be similar in all patients. On the day of the accident the thickness of the tendon was 9.3 mm. Four weeks later a remarkable regeneration could be seen in all patients (12.0 mm), which reached a maximum (16.7 mm) after 26 weeks. By the end of the study, however, the result was a scarred and thickened tendon of 11.5 mm. The comparison of the ultrasound results and the clinical examination after 26 weeks and 2.5 years showed no correlation between the value of the echo structure and functionality of the tendon, and the comparison between the different therapy groups showed no significant difference in the healing process either. In conclusion, ultrasound examination is able to provide information concerning the stage of the healing process. The quality of the healing and healed Achilles tendon and the relationship to their function cannot be studied with ultrasound, and this is not influenced by the choice of therapy.