Outcome of physical therapy for patients receiving workers' compensation may be related to a variety of factors, including the presence or absence of herniated lumbar intervertebral disc. The purpose of this study was to determine the level of disability, physical impairment, and rate of return-to-work for patients with disc disease and for those with mechanical low back pain syndrome without evidence of disc lesion. Twenty patients with disc disease and 22 patients with mechanical low back pain syndrome participated in this study. Physical therapy consisted of multiple interventions, including manual therapy based on the pattern of motion-provoked symptoms. The Oswestry disability questionnaire, fingertip-to-floor distance, and maximum pain-free isometric static lift were measured at the initial evaluation, 1 month following the initial assessment, and at discharge from the clinic. Patients with disc disease did not show significant improvement in the mean Oswestry score or in forward bending, but did show increased static lift capacity. In contrast, patients with mechanical low back pain syndrome had a significant reduction in disability and significant improvements in fingertip-to-floor distance and maximum pain-free isometric static lift. At the time of discharge, 90% of the patients followed with mechanical low back pain syndrome returned to work in some capacity compared with 45% of the patients followed with disc disease. A physical therapy program with multiple interventions that includes treatment based on the pattern of motion-provoked symptoms appears to have the greatest benefit for patients with mechanical low back pain syndrome.