We treated 20, steroid resistant or steroid dependent and cyclophosphamide or chlorambucil treated, relapsing nephrotic patients with oral cyclosporine A for eight weeks. Cyclosporine A was started at 7 mg/kg/day and titrated to maintain HPLC level of 100 to 200 ng/ml. Of 20 patients, 14 had a complete remission and the remaining 6 had a reduction in their proteinuria. The mean serum albumin of the 14 responders rose from 2.1 g/dl to 4.1 g/dl (P less than 0.00001) after cyclosporine A therapy. The mean serum cholesterol of the 14 responders decreased from 394 mg/dl to 184 mg/dl (P less than 0.0001) after cyclosporine A therapy. The mean creatinine clearance of the 20 patients (104 ml/min/1.73 m2) was unchanged (107 ml/min/1.73 m2) after eight weeks of cyclosporine A. By life table analysis, 40% of the responders show a sustained remission of up to a year. Cyclosporine A responders had a higher T3 cell count prior to therapy compared to nonresponders (69 +/- 5.54% vs. 61 +/- 6.4%, P less than 0.02). Pre-therapy interleukin-2 levels measured in 10 patients were normal or supranormal in 8, 6 of whom were treatment responders. Two patients with low interleukin-2 levels were nonresponders. Cyclosporine A can be used to induce a remission in relapsing nephrotic patients, and short-term cyclosporine A therapy does not produce nephrotoxicity.