We performed a magnetic resonance imaging (MRI) study in 16 consecutive patients who had undergone open repair of a unilateral Achilles tendon rupture (ATR) at an average of 32.5 (SD 3.2) (range 29-36) months from the operation. We measured the widest antero-posterior diameter of the tendon, the longest distance between the insertion of the Achilles tendon on the calcaneum and the musculo-tendinous junction of the soleus muscle on the Achilles tendon, the distance between the insertion of the Achilles tendon on the calcaneum and the point of maximal width of the tendon. We also ascertained whether areas of altered signal were present in and around the tendon. The operated tendons were always significantly thicker than the non-operated ones. There was a non-significant trend for the other measurements to be greater in the operated tendons. In five patients, areas of dishomogeneous signal were present in the operated tendon. These areas were less than 25% of the antero-posterior diameter of the tendon, and were clinically silent. These findings probably represent normal features of long-term tendon healing following open repair of an ATR.