Thirty-five cases of osteochondritis dissecans of the talus, operated on between 1950 and 1978, were studied. Twenty-four were available for follow-up an average of 47 months later. Three standard surgical approaches were used, and the osteochondritic fragment removed. In some cases the base of the defect was drilled. Good results were obtained in 15 patients, and fair in nine. There were no poor results. It was concluded that the defect is caused by trauma; that early operation gives the best results, 12 months being the critical delay time; that drilling the base of the defect improves results; and that the sex of the patient and the location of lesion are of little significance.