The authors report clinical, laboratory, and radiological results obtained by immunodepresant treatment of 78 patients suffering from rheumatoid polyarthritis, over a period of more than 4 years. In 27 of the patients the treatment had been followed for 4 to 8 years. Clinically the results were excellent in 36 cases, reasonably good in 23 cases; in 19 cases therapy was unsuccessful or had to to be stopped. There was a reduction in the sedimentation rate in cases with good results and in half the cases there was a reduction in the titre of the Waaler-Rose reaction. Studies on the evolution of radiological signs in 34 patients showed definite deterioration in only 2 cases out of 19 subjects having very good clinical results and definite deterioration in 7 of 15 subjects with less good clinical results or failure. Thus the immunodepressant treatment appeared capable of stopping or slowing down the osteoarticular destruction. The cessation of treatment in 28 patients was followed by a relapse in 14 patients (7 within 6 months, and 7 within 6 months to 2 years). In 14 patients there was no relapse and in 8 of these the improvement has lasted for more than 3 years. With the doses used, there were few short-term complications of treatment. Haematological tolerance appeared to vary according to the patient ; for prolonged treatment the dose should be adapted to the individual.