We reviewed thirty-seven hands of 26 patients with radial ray deficiency. Twelve patients (46%) had associated anomalies in extremities and/or other systems. Following Blauth's method, we classified patients into five groups. There was a positive correlation between the severity of the dysplasia of the thumb and the radius. Twelve hands of 10 patients were surgically treated. The mean follow-up time was 45 months. Only six hands had satisfactory cosmesis and function after surgery. We discuss the difficulty of treatment for severe cases.