Limitation of straight-leg raising (SLR) (Lasègue's sign) is considered an important test in the diagnosis of herniated lumbar disc disease. In a prospective study of 55 patients suffering from unilateral sciatica this sign was evaluated. Two aspects were investigated: 1) the interobserver variation, and 2) the correlation between the result of the test and the surgical finding. There was considerable interobserver variation among three observers concerning the measured angle at which pain was elicited. However, in 2/3 to 3/4 of the cases the variation amounted to 10 degrees or less. There was also some discordance in the classification of the type of pain that was elicited. Fifty-two patients underwent surgery; 45 had a prolapsed disc. SLR was "positive" in 49 cases, 43 of whom harbored a prolapsed disc. Crossed SLR was noted in 20, 19 of whom had a prolapsed disc at surgery. Absence of SLR limitation does not preclude the presence of a herniated lumbar disc.