Résumé : STUDY DESIGN: An epidemiological cohort study. OBJECTIVE: To describe the impact of psychosocial factors, both work and nonwork-related, on the prevalence of low back pain (LBP) after 6.6 years on average. SUMMARY OF BACKGROUND DATA: There is growing consensus that psychosocial factors play a role in the development of LBP, although results are not consistent across studies. METHODS: Within a sample of 2556 middle-aged men and women from the Belstress study, baseline psychosocial factors were measured through self-administered questionnaires and related to prevalent cases of LBP after a mean time interval of 6.6 years through Cox regression analysis. RESULTS: After adjustment for individual and physical risks, including occasional back pain at baseline, the prevalence rate of LBP in men is significantly related to baseline low decision latitude and low social support at work, and nonsignificantly to high job strain, low wage and job satisfaction, feeling stressed at work, and feeling depressed. High job insecurity, feeling stressed at work, and feeling depressed nonsignificantly increase the relative risks for LBP in women. CONCLUSIONS: Based on the results of this study, psychosocial factors (both work and nonwork-related) constitute nonnegligible risks for the development of LBP.