RATIONALE AND OBJECTIVES. Quantitative dynamic computed tomography was used with perfusion imaging to characterize intrarenal variations in perfusion in normal and abnormal human kidneys. METHODS. Perfusion images were obtained from 14 normal and four abnormal kidneys, comprising a renal tumor, an infarcted renal allograft, and two kidneys in a patient with cyclosporin toxicity. RESULTS. Images demonstrating quantifiable intrarenal variations in perfusion were consistently obtained. Normal cortical and medullary perfusion were 4.7 mL/min/mL and 1.1 mL/min/mL, respectively, consistent with accepted normal ranges. The changes in the abnormal kidneys corresponded with known pathophysiology. CONCLUSION. Computed tomography perfusion imaging creates quantifiable images of renal perfusion with a spatial resolution currently higher than any other functional imaging technique. It offers the opportunity to characterize renal diseases by their relative effects on cortical and medullary perfusion.