Forty adults with a history of Legg-Calve-Perthes disease treated with spica casts were clinically and radiographically evaluated an average of 30 years post-treatment (range 14 to 40 years). Clinical results were 85% good, 5% fair, and 10% poor. Five percent showed significant degenerative joint disease on follow-up radiographs and 7% had undergone prosthetic replacement. Fifteen percent of the patients had a positive family history of Perthes disease. Factors associated with a better result included: diagnosis before age 9, shorter length of follow-up, minimal femoral head and neck involvement, and a congruous joint.