112 patients with idiopathic childhood nephrotic syndrome have been referred from 1970 through 1989 at the Department of Pediatrics, University of Berne. One patient remitted spontaneously without medication. Ninety-eight patients responded to prednisone: 15 had a single bout of nephrosis, 47 developed a tendency towards relapses and 36 steroid dependence. In 28 patients with tendency towards relapses cure took place on either prednisone alone or prednisone plus cyclophosphamide. In 18 patients with steroid dependency cure took place on prednisone alone or prednisone plus cyclophosphamide. Thirteen patients failed to respond to steroids. The course of the disease was more benign in 68 patients with minimal change disease as compared with 14 patients with focal and segmental glomerular sclerosis. Immunofluorescence studies demonstrated mesangial IgM deposits in 14 out of 54 patients, but this finding was not a marker for poor steroid response or progression to renal failure. The course of the disease was especially unfavourable in patients with persisting nephrosis on completion of the initial course of steroid therapy. In conclusion it appears appropriate to define the disease in terms of steroid responsiveness as steroid resistant patients sometimes show normal glomeruli, steroid responsive sometimes have focal and segmental glomerular sclerosis or mesangial IgM deposits, and decisions depend more on the steroid responsiveness than on the histological features.