Renal injury from vesicoureteric reflux (VUR), or reflux nephropathy (RN), is a major cause of hypertension and end-stage renal disease and the only such cause which may be preventable. RN must have its onset in infancy or early childhood because renal scarring from VUR +UTI is observed rarely after childhood. While it is common to have renal scarring associated with severe grades of VUR, two prospective studies in children have found no benefit to early surgical correction of VUR over that of medical management. It has been assumed previously that mild and moderate (M/M) grades of VUR resolved spontaneously and were associated rarely with renal injury in the absence of UTI, but no such prospective study has been conducted to confirm this notion. Such a study was initiated 4 years ago with partial funding through NIH. The goals of the study are to observe over a 5 year follow-up period the evolution of M/M VUR by annual cystograms, to assess renal growth and injury by planimetric measurements from intravenous pyelograms at 1,3 and 5 years after diagnosis, to evaluate renal function by GFR, urinalysis and concentrating capacity, and to monitor blood pressure and measure plasma renin activity as predictors of hypertension in infants and young children < 5 years old at diagnosis and treated medically. When the study was closed to new patient entry, a total of 113 patients had been entered: 96 have completed first year, 59 second year and 21 third year follow up evaluations to date. While VUR improved or disappeared in 40% of ureters and only 2 previously normal kidneys had scars at 1 year (2/96 patients), 3 kidneys have scars and 5 others have exhibited poor growth or have evidence to suggest scarring at 3 years (8/21 patients); no relationship to the grade of VUR and scarring was observed in these patients. While all affected kidneys may be clustered in the first patients entered for the study, the importance of complete, long-term follow up of all patients is obvious. To accomplish this, the project must be funded adequately for 3 additional years. There has never been a similar prospective study of such a homogenous population with mild-moderate VUR. The conclusions of this study will either support current recommendations for conservative medical management of mild-moderate VUR in infants and young children or give reason to investigate management alternatives to reduce the incidence of serious consequences of a childhood disease which has its sequelae during adolescence and young adulthood.