Four cases of congenital radioulnar synostosis in three patients were treated by rotational osteotomy of the distal radius. The diaphysis of the radius was osteotomized transversely, and then the forearm was supinated manually. Following surgery, the palm was immobilized in a fully supinated position by a long-arm cast. The average age at surgery was 4 years 5 months old (range 3 years 11 months to 4 years 11 months), and the average follow-up was 21 months (range 12-36 months). Bone union was obtained in all patients without any complications or correction loss. Functional improvements were achieved in all patients. This procedure is simple and safe in the treatment of congenital radioulnar synostosis.