Ultrasonic renal volume and length measurements are easily performed in pediatric patients. Increases in volume over the normal level provide a potentially attractive method of assessing the severity and progression or regression of renal diseases. However, an analysis of data on 59 children with clinical renal disease and nephromegaly did not demonstrate any correlation with severity of the disease. We conclude that increases in renal length and volume in pediatric patients may indicate the presence of disease but not its severity.