Simple bone cyst is a benign bone tumor occurring most frequently in the long bone. The pathogenesis is not yet fully known and there is no established mode of optimal treatment. In 1979, Scaglietti reported favorable results in the treatment of simple bone cyst with steroid injection. We have studied 23 cases of curettage with bone graft and 13 cases of steroid injection in 39 cases of histologically proven simple bone cyst in the department Orthopedic Surgery at College of Medicine Yousei University dating from Jan, 1970 to Jan. 1989. In 1 case out of 23 cases, there was no improvement in curettage with bone graft, and this cases was treated with steroid injection. There were 4 cases which did not receive any treatment except cast immobilization. In this case, the patient refused further treatment. The mean follow up period was 20.1 months and the results and conclusions were as follows:1. The average age of patients was 17.9 years, and incidence under 20 years was 74.4% The male to female ratio was 1.6 to l. 2. Twenty three cases were treated with curettage with bone graft. The average age of patients was 16.1 years, and there were 4 cases of recurrence of simple bone cyst (17.3% ). 3. Thirteen cases were treated with steriod injection. The average age of patient was 12. 1 years, and there was 1 case of recurrence of simple bone cyst(7.6%). There were 6 cases who were completely healed after one steroid injection, 3 cases after 3 injections, 1 case after 4 injection, and 3 cases who had a maximun of 5 injections. 4. The difference was statistically significant from equality (p<0.05). The steroid injection method is a more simple and a more safe procedure than curettage with bone graft, and can be done at the Out-Patient Department. Steroid injection may be repeated in persisting and recurrent simple bone cyst.