Pericarditis was a frequent echocardiographic finding in 20 HLA B27 positive patients with erosive, seropositive rheumatoid arthritis (RA) and in 20 B27 negative RA controls (35% and 30% respectively). There was no significant difference in echocardiographic 2-D or M-mode measurements between the groups. A 48 hour continuous electrocardiographic monitoring, showed that ventricular extrasystoles were more frequent (p less than 0.01) in the B27 negative patients. Pulmonary diffusion capacity was reduced in 25% of the patients in both groups. There were no association between clinical or laboratory data and the cardiac or pulmonary findings except for the finding of a higher frequency of treatment with corticosteroids in patients with pericarditis.