OMERACT (Outcome Measures in Rheumatology) is an independent initiative of international health professionals interested in outcome measures in rheumatology. Over the last 20 years, OMERACT has served a critical role in the development and validation of clinical and radiographic outcome measures in rheumatoid arthritis, osteoarthritis, psoriatic arthritis, fibromyalgia, and other rheumatic diseases. OMERACT is coordinated by an executive committee and supervised by a steering committee. OMERACT organizes consensus conferences every two years, and employs various other means to stimulate the development of consensus in outcome measurement within the context of musculoskeletal and autoimmune diseases.