OBJECTIVE The pathophysiology of hypogammaglobulinemia in nephrotic syndrome (NS) remains unknown. We evaluated the differences in the distribution of anti-bacterial antibodies and anti-viral antibodies, and those of immune antibodies and natural antibodies in steroid-sensitive NS. METHODS We examined the antibody status of 18 children who had routine vaccinations. The levels of immnunoglobulin G (IgG), the IgG subclasses, and the antibodies induced by vaccinations such as diphtheria-pertussis-tetanus and measles-mumpsrubella were analyzed in children with steroid-sensitive NS. RESULTS There was a positive correlation between the albumin and IgG values (r = 0.6, p < 0.01), and the four IgG subclasses were all evenly depressed in the nephrotic children during the acute stage of the disease. The antibodies induced by bacterial antigens were depressed and the seropositivity of anti-viral antibodies tended to be lower than those of age-matched control children during the acute stage. The depressed immune antibody status recovered rapidly in the remission stage of NS, despite corticosteroid treatment. CONCLUSIONS IgG levels correlated positively with albumin levels, and all antibodies, including immune and natural antibodies, were depressed in the acute stage of NS. Our results suggest that hypogammaglobulinaemia in NS may be associated with intravascular homeostasis of oncotic pressure.