The study was made of antiviral antibodies to respiratory viruses, mycoplasma, O-streptolysin, of qualitative and quantitative characteristics of bacteriuria in 52 patients with nephrotic syndrome (NS) due to glomerulonephritis against 18 NS control subjects without glomerulonephritis. Significant differences between the groups appeared in the titers of antibodies to Coxsackie and influenza A viruses. O-streptolysin. Persistence of viral latent infection in NS is suggested as well as a trigger role of viruses in the disease onset and that of other urinary inflammatory affections whose incidence is now on the increase.