The aim of this study was to compare immediate weight-bearing mobilisation with traditional plaster casting in the rehabilitation of non-operatively treated Achilles tendon ruptures. Forty-eight patients with Achilles tendon rupture were randomised into two groups. The treatment group was fitted with an off-the-shelf carbon-fibre orthotic and the patients were mobilised with immediate full weight-bearing. The control group was immobilised in traditional serial equinus plaster casts. The heel raise within the orthotic and the equinus position of the cast was reduced over a period of eight weeks and then the orthotic or cast was removed. Each patient followed the same rehabilitation protocol. The primary outcome measure was return to the patient's normal activity level as defined by the patient. There was no statistical difference between the groups in terms of return to normal work [p=0.37] and sporting activity [p=0.63]. Nor was there any difference in terms of return to normal walking and stair climbing. There was weak evidence for improved early function in the treatment group. There was 1 re-rupture of the tendon in each group and a further failure of healing in the control group. One patient in the control group died from a fatal pulmonary embolism secondary to a DVT in the ipsilateral leg. Immediate weight-bearing mobilisation provides practical and functional advantages to patients treated non-operatively after Achilles tendon rupture. However, this study provides only weak evidence of faster rehabilitation.