Rheumatoid arthritis is present in a population which is heterogeneous both clinically and immunologically. A variety of cells including lymphocytes, macrophages and fibroblasts play important roles in its pathogenesis, but the T cell appears to be a common thread throughout the disease process. Treatments aimed at reducing these lymphocytes mechanically and specifically result in a good clinical response in many patients. The mechanism of action of cyclosporin A (CyA) in inhibiting T lymphocytes presents a more specific form of therapy. The effects of CyA on the activity of RA have mainly been investigated in patients with active, refractory long-term disease. The data obtained in these trials suggest that CyA is not only a symptomatic treatment for RA but can also be considered a DMARD. The potential benefits of CyA on the one hand and its potential toxicity on the other indicate that a careful assessment should be made of its use in patients with early active RA.