To evaluate the usefulness for the diagnosis of rheumatoid arthritis of tests for rheumatoid factors, antiperinuclear factors, antikeratin antibodies, and the HLA DR4 antigen, we retrospectively reviewed the medical records of 138 patients consecutively admitted to our rheumatology department between January 1, 1988 and December 31, 1990 for evaluation of peripheral inflammatory joint manifestations. Each patient had a standard work-up including a physical examination, laboratory tests, and roentgenograms. In 1994, after a follow-up of three to six years, the final diagnosis was rheumatoid arthritis in 39 patients and another well-defined disorder in 63; no diagnosis was established in 36 patients, among whom nine were lost to follow-up. The decreasing order of diagnostic usefulness was antiperinuclear factors, HLA DR4, rheumatoid factors (latex test), and antikeratin antibody. The likelihood of rheumatoid arthritis was greatest in those patients with positivity of two of the three following markers: rheumatoid factors, antiperinuclear factors, and the HLA DR4 antigen.