The radiological findings in a cohort of 138 adults with chronic pyelonephritis are presented and the following conclusions made. (1) Scarring is commoner in the right kidney than the left and is found in the upper, middle and lower poles with decreasing frequency from above down. (2) Agreement between observers in the grading of scarring in urograms taken without standardisation or routine tomography, is sufficiently high to justify the continued use of the intravenous urogram as a screening test but is not high enough to detect any progression of scars in the group over a 6.5-year period. (3) Repetition of urograms seldom reveals the development of calculi or other new abnormalities and is not justified as a clinical routine. (4) The combination of extensive bilateral renal scarring and proteinuria is associated with the worst renal function.