Pooled indices of several measures have been developed to assess and monitor patients with rheumatoid arthritis in clinical trials and clinical care, as no single measure can serve as a "gold standard" in all individual patients. Early indices of disease activity include the Steinbrocker "therapeutic scorecard in rheumatoid arthritis," the Lansbury Index, and Paulus criteria. The most widely used indices at this time are the American College of Rheumatology (ACR) Core Data Set and disease activity score (DAS). A simplified disease activity index (SDAI) and clinical disease activity index (CDAI) are derived from the DAS. The ACR Core Data Set includes 7 measures--swollen joint count, tender joint count, patient assessment of global status, an acute phase reactant [erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP)], health professional assessment of global status, physical function, and pain; the first four of these measures are included on the DAS. Improvement criteria for the ACR Core Data Set are based on improvement of at least 20% in both tender and swollen joint counts, and three of the five additional measures (ACR 20), and corresponding "ACR 50," and "ACR 70." A pooled index which includes only the three patient self-report questionnaire measures from the Core Data Set, physical function, pain, and patient assessment of global status performs as well as ACR 20 or DAS to discriminate between efficacy of active versus placebo treatment in a clinical trial.