Twenty-one children with idiopathic nephrotic syndrome and minimal changes on renal biopsy were followed during all the disease. The average of follow-up was 37 months, with a range from 12 to 124 months. Recurrent proteinuria was the most important feature during the follow-up; 14 out of the patients showed frequent relapses, but only 2 patients showed major complication (peritonitis, septicemia) during relapses. Frequent relapses appeared most frequently in patients who began the disease before their fourth birthday, showed allergic history, had hypertension and red blood cells in urine, or had recurrent infections and finally, in those where proteinuria reappeared soon after prednisone therapy was ended. Prednisone alone was successful to induce remission, but it did not prevent frequent relapses. The association clorambucil-prednisone allowed lengthening of the period of remission and possibly for this reason the rate of relapses fell during the first 37 months of the follow-up. There are no signs which permit to predict the length of the disease and the frequent relapses can occur even after many years from the beginning of the disease. Special care of these patients avoids major complications.