Cross-cultural adaptation and cross-sectional psychometric testing. To develop and validate a cross-cultural version of the Roland-Morris Questionnaire for use in German-speaking patients with low back pain. Clinical research related to the management of back pain would be facilitated enormously if a small number of patient-oriented questionnaires became widely used. If the transposition of a questionnaire from its original cultural context is done by simple translation, it is unlikely to be successful because of language and cultural differences. Therefore, a simple direct translation of a questionnaire from one language to another does not permit its use in clinical trials. The instrument was translated and back-translated, pretested, and reviewed by a committee. The German version of the Roland-Morris Questionnaire was tested in 125 patients with low back pain. The study was conducted at the spa resort at Senftenberg, Austria, which is visited by patients from all countries of German-speaking Europe. Reliability and concurrent construct validity were assessed with Pearson's correlation coefficient on the Roland-Morris Questionnaire scores compared with the scales of the Medical Outcome Study Short Form-36 questionnaire. Pearson's correlation coefficient for test-retest reliability of the German version was r = 0.82 (P = 0.0001), and Cronbach's alpha was 0.81. The concurrent validity was r = 0.81 (Roland-Morris Questionnaire/pain rating; P = 0.0001), r = 0.48 (Roland-Morris Questionnaire/forward bending; P = 0.0001), and r = -0.47 (Roland-Morris Questionnaire/lateral bending; P = 0.0001). Correlation between the functional scales of the Medical Outcome Study Short Form-36 questionnaire and the Roland-Morris Questionnaire sum scores ranged from r = -0.29 (emotional limitations; P = 0.0011) to r = -0.71 (physical limitations; P = 0.0001). Because the German version of the Roland-Morris Questionnaire seems to be reliable and valid for the assessment of the functional status in German-speaking patients with low back pain, the use of this translated instrument can be recommended in future clinical trials.