BACKGROUND AND PURPOSE: Psychosocial factors are known to affect recovery from acute low back pain. The factors with the greatest influence and the optimal methods of measurement and interpretation have not been established. The purpose of this study was to examine baseline psychosocial variables and their ability to predict prolonged work restrictions. SUBJECTS: The subjects were 78 people with work-related low back pain who were participating in a clinical trial (mean age=37.4 years, SD=10.4, range=18-58; mean duration of pain=5.5 days, SD=4.6, range=0-19). METHODS: A baseline examination including measures of impairment, disability, and psychosocial variables was performed. All subjects had physical therapy interventions. Work status was assessed after 4 weeks. Sensitivity, specificity, and likelihood ratios were calculated for the prediction of work status by the use of psychosocial variables. Receiver operator characteristic curves and logistic regression were used to identify the variables that were most predictive of work status. RESULTS: Twenty-two subjects (29%) had persistent work restrictions. The work subscale of the Fear-Avoidance Beliefs Questionnaire was the strongest predictor of work status (negative likelihood ratio of 0.08 for scores less than 30, positive likelihood ratio of 3.33 for scores greater than 34). DISCUSSION AND CONCLUSION: Fear-avoidance beliefs about work was the psychosocial factor that could best be used to predict return to work in patients with acute work-related low back pain. Examination of fear-avoidance beliefs may serve as a useful screening tool for identifying patients who are at risk for prolonged work restrictions.