A specially designed inclinometer has been used to measure one part of the clinical deformity (asymmetry of the trunk) that is seen in scoliosis. This objective measurement provides one good guideline that can effectively determine, in surveys of children, whether or not further orthopaedic evaluation is needed. A minimum significant angle of trunk rotation of 5 degrees was shown by computer-analyzed data from 1,065 patients to be a good criterion for identifying curvatures of 20 degrees or more. The specificity of scoliosis screening in this manner has a projected false-negative rate of 0.1 per cent and a high degree of sensitivity. The method is simple, reliable, and inexpensive. It is easily taught to lay personnel who can be employed in scoliosis screening procedures.