It is now becoming increasingly evident that pyelonephritis is one of the more common bacterial infections in infants and children leading to serious consequences if uncontrolled. In the chronic form it may cause serious impairment of renal function with resultant growth failure, renal rickets, uremia, hypertension, and death in the older child and young adult.1-3 In the acute phase it may act as a focus for sepsis,4 and often it may be a serious and life-threatening complication of a variety of other conditions. Presently, with refined techniques of bacterial colony counts on urine and urinary tract visualization, the great incidence and prevalence of the disease are being appreciated more and more.5 An increasing number of morbidity studies are being published, but there is still a dearth of autopsy studies with pathologic data available. We thought it would be of value and interest to examine the experience over