Fifty-seven patients treated for an acute rupture of the Achilles tendon were studied. The patients were randomized into a Mason suture technique or a reinforced continuous six-strand suture technique, and markers were attached to each tendon end perioperatively. The postoperative separation of the markers was studied by repeat radiographic examination. Despite immobilization, separation developed after a biphasic course, and after 7 weeks the mean separation was 10.5 mm. No difference was found between the two techniques. We attempt to correlate the separation to the clinical outcome, examined at 1 year follow up.