We describe an index of functional impairment and a system of scoring joint tenderness for use in the assessment of ankylosing spondylitis. The functional index consists of 20 questions and the articular index is based on the scoring of a total of 10 joint responses after movement or firm digital pressure. These indices are simple to establish and not time consuming. They have a high degree of intra- and interobserver reproducibility. The indices showed changes in short term clinical trials of antiinflammatory drugs; these changes were highly correlated with the patient's overall assessment of his own clinical condition.