Ninety-four rheumatoid patients were studied through laboratory, clinical, algometric, functional and psychological parameters (29 variables in all). Using factorial analysis, four factors emerged which explained 74% of the common variance. The four factors were: the disability factor (explaining 39% of the variance); the biology factor (explaining 21%); the algology factor (explaining 8%); and the clinical factor represented by the Ritchie Articular Index (RAI) (explaining 6%). The four items were used to construct a Chronic Arthritis Systemic Index (CASI) which correlated significantly with other indices, such as the Mallya-Mace, the Thompson and the limited Lansbury indices. CASI provided to be very useful in monitoring the disease course in a short term study of 22 patients undergoing DMARD treatment. Taking into account the parameters proposed as outcome measures by several workshops, CASI can monitor both the activity and severity of chronic arthritides through simple measures.