Thirty patients with osteochondritis dissecans of the ankle have been followed up for an average of 21 years. The histories and radiographs were reviewed, and it was found that most patients had only minor radiographic changes and symptoms. Two patients had developed osteoarthritis but in only one was this severe. Osteochondritis dissecans in the ankle thus seems to differ from the same lesion in the knee where late osteoarthritis often occurs. Two lesions were located on the joint surface of the distal tibia, a site not previously reported.