The retrograde flow of dye from the calices into the collecting tubules (intrarenal reflux) seen during cystrography in children and its effect on the kidneys were evaluated. A retrospective analysis was made of 175 patients with excretory urograms revealing cortical atrophy. Of these patients 68 per cent had cystograms revealing vesicoureteral reflux. Intrarenal reflux was seen in 8 patients less than 6 years old, an incidence of 13.5 per cent in that age group. There was a high correlation, 7 of 8 or 87.5 per cent, between the areas of intrarenal reflux, and associated renal cortical atrophy and calicectasis. Intrarenal reflux provides a pathway by which bacteria and hydrostatic pressure may produce injury to the renal parenchyma. The presence of intrarenal reflux is an absolute indication for ureteroneocystostomy.