Objective: This study examined pain and impairment beliefs [measured with the Pain and Impairment Relationship Scale, (PAIRS)] of chronic low back pain patients during rehabilitation and hypothesized that pain beliefs would be stronger in drop-out subjects, decrease during treatment, and after treatment correlate strongly with disability measures.Design: Prospective cohort.Setting: Outpatient, functionally oriented rehabilitation program for chronic low back pain.Patients: 72 consecutive chronic low back pain referral patients disabled from working because of pain.Involvement: Interdisciplinary rehabilitation with a focus on intensive physical reconditioning was employed.Outcome Measures: Program completion versus drop-out groups and pretreatment and posttreatment pain, disability, depression, and PAIRS scores were compared.Results: Thirty patients dropped out and 42 subjects completed treatment. The PAIRS scores at evaluation were similar for both groups. The PAIRS scores improved significantly during treatment (p < 0.001). Posttreatment PAIRS scores correlated highly with disability measures (r= 0.79, p < 0.001).Conclusion: Pain beliefs are of minimal value for predicting treatment compliance, but may be altered during functionally oriented treatment of chronic low back pain. Posttreatment disability closely mirrored attitudes and belief-associated pain and impairment.