A reproducible method of measurement of kyphosis in spondylolisthesis using the cranial surface of the fifth lumbar vertebra and the caudal surface of the first sacral vertebra is described. This measurement is useful in the prognosis of spondylolisthetic patients as the progression of slipping is determined by both the angle of kyphosis and degree of slip. The angle is also important in operative correction of spondylolisthesis. This method is readily used and reproduced in severe slips.