OBJECTIVES: (1) To investigate the measurement characteristics of the Hospital for Special Surgery (HSS) and Mayo Clinic elbow assessment instruments, utilizing methodological criteria including feasibility, reliability, validity, and discriminative ability; and (2) to develop an efficient and disease-specific rating system for elbow function assessment (EFA) in adult patients with RA, using a combination of self-reported subjective items and objective measures, and comparing its characteristics with the HSS and Mayo Clinic scales. METHODS: (1) Selection of elbow-specific items. (2) Investigation of reliability and validity of all separate items, as well as the total HSS and Mayo Clinic scores, in 42 patients with RA (mean age 60 yrs). Direct observation of functional elbow performance was defined as the gold standard against which criterion validity was compared. (3) Reaching agreement within a team of professionals on the different scale dimensions and the assigned weight. (4) Item reduction by eliminating unreliable, inaccurate, unfeasible, and ambiguous items. Finally, the EFA scale was constructed by selecting the most reliable and accurate items. RESULTS: The EFA scale showed a superior or equal degree of reliability as reflected in intraclass correlation coefficients of more than 0.88, and also superior validity, compared with the HSS and Mayo Clinic measures. CONCLUSION: Although the elbow scoring systems currently available provide a reliable measure, they seem restricted in evaluating elbow-specific functional ability. The EFA scale was found to be most suitable to measure elbow functional ability in RA, and was also shown to be highly reliable and practical in clinical practice.