Forty-four patients with early RA who had participated in a six months double-blind trial, comparing cyclosporine A (CsA) (n = 22) with chloroquine (Chl) (n = 22), were followed for a further 18 months irrespective of their treatment status. At two years follow up, the mean CsA dose was 2.7 +/- 1.1 mg/kg/day (n = 15) and the dose of Chl (n = 11) was 100 mg/day in every patient. Maximal difference in efficacy (represented by the percentage of patients who fulfilled the Paulus 50% response) was reached at one year (CsA group: 68% and Chl group: 36%; p = 0.07). At two years, the differences in efficacy and toxicity between the two groups had diminished. The conclusions of this follow-up study are: 1. maximal efficacy of low dose CsA in early RA patients is reached after one year of therapy. 2. CsA can maintain clinical efficacy and safety comparable to Chl for a period of at least two years.