The authors developed and validated a measure of health outcome for patients with low back pain. A questionnaire was developed incorporating the type of questions asked when taking a clinical history. After testing on a sample of 568 patients, three questions were discarded from the questionnaire. The final questionnaire was found to be reliable and valid in the sense that patients' scores correlated highly with their scores on a general health profile and with GP perceptions of severity. Health status in patients with low back pain was significantly impaired when compared with the general population. A clinically based questionnaire, together with a general measure of health, can provide a valid and reliable package for the routine assessment of perceived health in patients with low back pain.