Over the past several decades screening for disease in large asymptomatic populations has increased, culminating most recently with a federal mandate for early, periodic screening, diagnosis and treatment of all children from low-income families. The present study of five consecutive examinations in over 12,000 schoolchildren shows the cumulative occurrence of proteinuria and hematuria to be surprisingly high (greater than 6%). Comparison of this large number of children with the few individuals in whom death occurs from chronic renal disease annually (less than 0.03%) suggests that the vast majority of these children with urinary abnormalities have either no renal disease or at most a self-limited condition. Observation of 512 children with proteinuria and 78 with hematuria for one to five years after initial detection and referral to their physician or clinic provides a measure of both contemporary management and early natural history. These observations suggest that there is a need to question the overall effectiveness of urinary screening and that early inclusion of roentgenographic and urologic investigations in management seems unwarranted. Rather, these children should be followed for long periods of time. Additional investigations are indicated when worsening of the abnormal findings or other evidence of renal or systemic disease occurs. If routine urinary screening is performed, it should be as one aspect of a multiphasic program by the primary physician so that it can be coupled with a clearly defined plan for follow-up and management of subjects with abnormal findings.