To evaluate the prevalence and incidence density of heavy proteinuria and chronic renal insufficiency (CRI) and the factors related to disease progression, 10,288,620 urinary screenings of elementary and junior high-school students from 1992 to 1996 were studied retrospectively. Urinary screening included pH, protein, occult blood, and glucose measurements. Blood sample analysis included total protein, albumin, A/G ratio, blood urea nitrogen, creatinine (Cr), antistreptolysin O titer, C3, cholesterol, hepatitis B virus surface antigen, IgA, and fasting blood sugar. The results showed that the 4-year prevalence of proteinuria was higher in girls than in boys (6.87x10(-4) vs. 4.83x10(-4) respectively). There were 189 cases with disease progression into CRI among the 10,288,620 students screened and followed continuously, with the prevalence of disease progression into CRI higher in boys than in girls (2.24x10(-5) vs. 1.41x10(-5) respectively). Of the 119 cases (63%) presenting with CRI since the first urine screening and blood sampling, only 14 had serum Cr levels higher than 6.0 mg/dl. There were 1,289 patients (10.5%) with proteinuria in 1992 and 705 patients (7.1%) in 1996. The absolute number of patients with heavy proteinuria decreased. The percentage of underlying glomerulonephritis in children on dialysis also decreased from 63.2% in 1992 to 47.0% in 1996. Logistic regression analysis showed that a persistent serum cholesterol level higher than 220 mg/dl, an albumin level lower than 3.5 g/dl, total protein less than 6 g/dl, and diastolic pressure higher than 90 mmHg were the significant risk factors for disease progression to CRI. We conclude that early detection of students with heavy proteinuria by mass urinary screening, early appropriate treatment, and monitoring of significant risk factors may help to decrease or delay the progression of renal disease, delay the introduction of dialysis in these predialysis CRI patients and maintain their growth and development.