The American Rheumatism Association (ARA) 1958 and 1987 criteria for the classification of rheumatoid arthritis (RA) were applied to 111 consecutive RA patients and 54 patients with non-RA connective tissue diseases from three hospitals of tertiary level in Beijing. Comparison of the two criteria showed that the specificity was the same, being 88% for both, whereas the sensitivity varied from 94% of the 1958 criteria to 91% of the 1987 criteria. Factors affecting the sensitivity were morning stiffness for more than one hour and increase of number of swollen joints from one to three in the 1987 revised criteria.