Articular patterns of rheumatoid arthritis were determined based upon the numbers of joints found to be tender or swollen in 50 younger adult patients with early-diagnosed rheumatoid arthritis examined semi-annually over a mean interval of 5.7 years. Numbers of joints involved were analyzed according to (1) cross-sectional frequency distributions, (2) cumulative probability plots of each patient's linear regression slope during follow-up, and (3) clinically intuitive definitions of course patterns. These approaches converged on three articular patterns, that is, monocyclic, polycyclic, and progressive. Monocyclic course was observed more frequently in men, in patients without rheumatoid factor, and in those with the fewest numbers of joints involved at entry. Polycyclic course was the most common and characterized by a level regression slope of involved joints during follow-up, although fluctuating over time. This course could be subdivided into the intermittent (having at least one remission of joint involvement for at least six months) and the continuing patterns. Progressive course was least common and found in patients with the greatest numbers of joints involved at entry. These data indicate that articular patterns in rheumatoid arthritis are usually established within the early course of disease. Further study of the early course of rheumatoid arthritis should be pursued for proper understanding of its host determinants, prognostic factors, and optimal patient management.