['To determine whether the Work Ability Index (WAI), a short 7-item self-report questionnaire addressing issues of perceived disability, impairment, and expectations for resuming work, predicts application for disability pension, recommendations for further treatment, and other adverse work-related criteria in patients with chronic back pain after rehabilitation.', 'Cohort study with 3-month follow-up.', 'Seven inpatient rehabilitation centers.', 'Patients (N=294; 168 women; mean age, 49.9y) with chronic back pain.', 'The WAI was completed at the beginning of rehabilitation. All patients were treated according to the German rehabilitation guidelines for chronic back pain and work-related medical rehabilitation.', 'Application for disability pension, as assessed by a postal questionnaire 3 months after discharge.', 'Receiver operating characteristic curve analysis of the association between the WAI at baseline and subsequent application for disability pension revealed an area under the curve of .80 (95% confidence interval [CI], .62-.97). Youden index was highest when the WAI cutoff value was ≤20 points (sensitivity, 72.7%; specificity, 82.2%; total correct classification, 81.7%). After adjusting for age and sex, persons with a baseline WAI score of ≤20 points had 15.6 times (95% CI, 3.6-68.2) higher odds of subsequent application for disability pension, 4.9 times (95% CI, 1.5-16.8) higher odds of unemployment, and 6 times (95% CI, 2.4-15.2) higher odds of long-term sick leave at follow-up.'] Does work Ability Index predict application for disability pension after work-related medical rehabilitation for chronic back pain?