This study was designed to evaluate the validity of straight leg raising (SLR) test in the detection of a herniated disc at the slipped segment of a spondylolisthesis. The SLR test was performed preoperative on 60 patients with spondylolisthesis that showed no evidence of disc herniation at the non-slipped segments. Those patients with a positive SLR test (tension sign appeared at an angle less than 70 degrees) underwent exploration of the disc space at the slipped segment during the operative procedures (internal fixation and/or decompressive laminectomy) for the spondylolisthesis, while those with a negative SLR test underwent operative procedures without exploration of the disc space. Our results showed that nine patients (all showed a radicular pain) in the series delineated a positive SLR test. Among them, 6(67%) were proven to have a herniated disc at the slipped segment and 3 were found to have a stenotic lateral recess due to hypertrophied yellow ligament. Both of the two patients with a positive SLR test measured at an angle less than 30 degrees, had a herniated disc at the slipped segment. In 51 patients showing a negative SLR test, 3 had persistent radicular pain after the operative procedures without exploration of the disc space. As they refused a subsequent operation, it was uncertain whether they harbored a concomitant disc herniation or not. If patients free of radicular pain after an operation without discetomy were considered as not having a concomitant symptomatic herniated disc, our result implied that at least 48 (94%) of the 51 patients with spondylolisthesis showing a negative SLR test did not have a symptomatic disc. Statistical analysis showed that SLR test is significantly associated with disc herniation in spindylolisthesis (fisher's exact test; two sided; p=0.0001).