This prospective study investigated the relationship between behavioral sign scores [from Waddell) and the return to work status of chronic low-back pain patients who completed a work-oriented physical rehabiliation program without formal facility-related psychologic or social services. Further, the authors monitored the effect of this program on changing these scores. The program consisted of physical reconditioning through resistive exercises, flexibility and aerobic training, posture end body mechanics education, and progressive work simulation tasks and activities of daily living. One hundred eighty-three nonworking or partially disabled low-back pain patients with an average duration of 8.7 months' disability were included in the study. The presence of each of eight behavioral signs was tested for an entry end again on completion of the program. Analysis showed a significant drop in behavioral sign scores for patients who successfully returned to work. There was no significant reduction in scores for patients who did not return to work. The results suggest these signs may predict the effectiveness of treating chronic low-back pain patients in a return-to-work physical rehabiliation program, Conversely, screening for behavioral signs may identify low-back pain patients who would benefit from intensive behavioral end psychiatric testing and intervention efforts.