Relapses are important problems in minimal change disease which accounts most of the cases in childhood nephrotic syndrome. Infection is the most important complication that determines mortality and morbidity. Because of defects in humoral immune system, patients are predispose to infections in nephrotic syndrome. In this study, serum levels of IgG and its subclasses were studied to evaluate the relationships between the nephrotic syndrome and infection on 17 children with nephrotic syndrome (24-96 months of age) and 10 healty children (27-84 months of age). At the end of this study, serum levels of IgG and its subclasses were found to be lower in active disease group than the contol group. However, these values were lowest for the infection group. Although it was observed that these values increased with steroid treatment , they did not reach to normal levels. The parameters in the remission were not different from the parameters in control subjects.