To determine the effects of T cell vaccination (TCV) in patients with rheumatoid arthritis (RA), thirteen RA patients were inoculated with attenuated synovial T lymphocytes which contain the putatively pathogenic cells. The procedure was technically feasible and free from toxicity. Variable clinical and immunological responses were found. However, in one patient with recent onset disease and treated with a defined T cell clone, a temporary beneficial response coincided with depressed mitogen reactivity and a decrease of rheumatoid factors. This study may serve as a lead for future research on TCV in humans.