This paper describes a simple method for the recording of rib deformity in idiopathic scoliosis. The relationships have been recorded between the measured rib hump and rib depression deformities and 1) the rotation of the vertebral bodies (as measured by the method of Nash and Moe on the standing radiograph); 2) the degree of lateral curvature (as measured by the method of Cobb on the standing radiograph); and 3) the rib-vertebra angles and their differences (as described by Mehta). No clear linear relationships were found. Many examples of irregular relationship were recorded, for example, marked spinal rotation with minimal rib hump. The response of the rib deformities to treatment by Milwaukee brace in fifty-two patients is described; the hump is little changed but the depression on the opposite side may be considerably reduced. Harrington instrumentation may have a similar effect.