Thirty-three children with steroid-dependent or steroid-resistant idiopathic nephrosis were treated with a combination of cyclophosphamide and prednisone. Remission occurred in all 23 steroid-dependent patients and, at last report, 12 had gone without any medication for periods of from two months to 21 months without relapse. Remission occurred in five of ten steroid-resistant patients. The renal biopsy findings in these patients demonstrate a correlation between the "minimal change" lesion and a positive response to cyclophosphamide.