A program of urine screening for asymptomatic hematuria and proteinuria in school children has been conducted since 1973 by the Ministry of Education in Japan with great success in the early detection of asymptomatic renal disease. In order to know whether this nationwide program during 13 years has contributed to understanding of the epidemiology of chronic glomerular disease in Japan, a multicenter survey of the patients was conducted. Between 70% and 80% of IgA and non-IgA mesangial proliferative glomerulonephritis and 65%-80% of membrano-proliferative glomerulonephritis (MPGN) were detected by mass urine screening at school. Severe glomerular lesions were more frequently observed in children with chance proteinuria and hematuria, as well as IgA and non-IgA mesangial proliferative glomerulonephritis with significant proteinuria. Mild glomerular change was more frequent in patients with MPGN, IgA and non-IgA mesangial proliferative nephritis with minimal proteinuria who were detected by our screening program, rather than those seen with some of the nephritic signs and symptoms at diagnosis. The above evidence suggests that a screening program may open the way for the early management of these diseases, especially where treatment is already established.