The treatment of bone cysts by topical injection of methylprednisolone acetate was initiated at the end of 1973, and the late results are reported in this paper. In seventy-two cases followed up for one to three years favourable results have been obtained in about 90 per cent. The technique of local injection and the surgical equipment employed, in the case of focal recurrences, are considered. With this method, surgical treatment of bone cysts in youth is seldom necessary.