Quantification of human performance in chronic low back pain (CLBP) patients is essential to initiate effective treatment and guide progress in a disability-oriented functional restoration program, as well as to objectively evaluate impairment and functional limitations at the time of maximum medical improvement. One such important measure of physical ability is range of motion. Patients who suffer from CLBP almost invariably have some distrubance of mobility. The major goals of the present study were to: 1)develop a database of anticipated range of motion levels at different points in time in a representative sample of CLBP patients; 2) within the sample, determine any gender or spinal surgery-induced differences; 3) evaluate change in range of motion produced by participation in a comprehensive functional restoration treatment program: and 4) identify residual impariment of regional range of motion. Four separate groups of CLBP patients were evaluated; Group 1 (n =92), unoperated men; Group 2 (n = 26), postdiscectomy men; Group 3 (n = 59), unoperated women; and Group 4 (n = 17) postdiscetomy women, Patients in each group were assessed for spinal range of motion measures at three points in time, for sagittal/coronal motion and validity (employing the relationship between pelvic motion and supine leg raising). Results demonstrated dramatic patient improvements in range of motion from initial referral to program completion, The most significant gains were made in pelvic motion, which returned to near normal levels, indicating that the vast majority overcame low effort or movement inhibition produced by pain or fear of injury. Poor effort initially shown by 28% of patients (PRE) dropped to 3% at post-study re-evaluation (FU). However, biplanar true lumbar motion generally remained mildly restricted, most significantly in the postdiscectomy group, consistent with a degree of persistent (and, possibly, permanent) Impairment of mobility, There were also no significant differences in final true lumbar flexion/extension scores between male and female patients, as was previously shown for normal subjects. In summary, it appears that surgery has more of an effect on patient response to functional restoration treatment than gender. These data will provide clinicans with a valuable resource for gauging expected progress in patients undergoing effective fucntional restoration treatment for disabling CLBP, and will identify expected pretreatment motion inhibition and post-treatment permanent (or persistent) residual impairment of regional T12–81 mobility.