Ninety six patients aged from 6 months to 15 years and were admitted to Chilean hospitals with the diagnosis of primary nephrotic syndrome in a period of 30 months. These patients were randomly separated in two groups, group A received prednisone for 8 weeks and group B received the same drug during 12 weeks. All patients were evaluated at 6, 12 and 18 months after the end of treatment. The moment and number of relapses per patient, accumulated percentage of relapses, relapse rate per 100 patients, total number of relapses and complications were assessed. Frequent relapsers were subjected to a kidney biopsy, leaving in the protocol only those patients that had minimal changes. Patients resistant or dependent to steroid therapy were discarded. Thus we report the results of 56 treated patients followed during 18 months. No differences in analyzed parameters were observed between the two treatment groups. It is concluded that these preliminary results do not support the prolongation of prednisone treatment in children with primary nephrotic syndrome.