In a cohort of 919 patients with definite or classic rheumatoid arthritis followed prospectively since 1966, we identified 36 patients with Felty's syndrome (FS). Their clinical course was compared to that of 72 matched controls from the same cohort. Patients with FS had more extraarticular features and more infections than control patients. The presence of joint erosions, serial Lansbury indices, and death rates were similar in both groups. Cardiovascular disease was the commonest cause of death in both groups, accounting for 32% of all deaths. Sepsis accounted for 10% of deaths in the group with FS and 13% of deaths in the controls.