We studied the distribution and characteristics of circulating rheumatoid factors (RF) and anti-nuclear antibodies (ANA) in 30 rheumatoid arthritis (RA) patients who had polyarthritis alone (group I), 28 RA patients with polyarthritis and extra-articular disease (group II), 28 RA patients with systemic vasculitis (group III) and 60 healthy matched controls. IgG RF occurred more frequently and in higher serum titres in group III (100%) than RA patients in group I (40%), or in group II (18%) or in normal controls (5.8%). The serum titre of IgM RF was higher in vasculitis patients than in other RA patients. ANA were found in 74% of all RA patients and although the frequency did not differ in the three patient groups, the serum titre was significantly higher in the vasculitis group. Antibodies to extractable nuclear antigen were found only in group III (18.7%). Antibodies to histones were also more prevalent in group III than in the other RA groups. The serological abnormalities in rheumatoid vasculitis differed quantitatively as well as qualitatively from other RA patients.