Sixteen lymph nodes from 14 patients with rheumatoid arthritis were examined immunohistochemically and morphometrically and compared with 10 control nodes showing follicular hyperplasia from patients without rheumatoid disease. Frozen material was available from nine patients and all controls. The nodes from patients with rheumatoid arthritis seemed to share characteristic features. The most striking of these was follicular hyperplasia in which the germinal centres, in spite of being quite large, showed relatively sparse proliferative activity. The nodes often showed infiltration of germinal centres by CD8 positive T lymphocytes and contained fewer IL2R positive cells in the paracortex than controls. These and other features may have some correlation with disease activity. Lymphadenopathy in rheumatoid arthritis may not just be a manifestation of joint inflammation but an active component of this multisystem disease and may reflect a widespread immunological abnormality.