We conducted a study to determine if effective renal plasma flow routinely measured by hippurate clearance during a comprehensive renal scintillation procedure is a relevant measure for assessing renal function in spinal cord injury patients. All subjects had spinal cord injury and had had contemporaneous comprehensive renal scintillation procedures and excretory urograms on 2 occasions 24 months or less apart. Each of the 469 kidneys was placed into 1 of 5 quintiles on the basis of its effective renal plasma flow at the first examination. The percentage of the kidneys that had clinically significant pyelocaliectasis or in which the pyelocaliectasis significantly worsened was 20.4 per cent in the lowest (first) quintile and 9.3, 2.2, 5.4 and 3.2 per cent in the second, third, fourth and fifth quintiles, respectively. Analogous data for ureterectasis were 16.1, 8.2, 2.2, 3.3 and 3.2 per cent. There was a significant (p less than 0.01) correlation between effective renal plasma flow and renal parenchymal thickness. Kidneys with renal calculi averaged effective renal plasma flows about 25 per cent lower than those of kidneys free of calculi. We conclude that effective renal plasma flow is a relevant measure for assessing renal function in spinal cord injury patients.