The aim of this study was to determine if an area of decreased color on color Doppler energy scans in a transplanted kidney could be related to significant pathologic conditions. Three hundred and ninety-eight scans in 150 patients were thus evaluated prospectively, and 12 such areas were found and correlated to B-mode, spectral, and color Doppler sonography as well as clinical and laboratory findings. A cause for the hypoperfused area was found in all cases; causes included two cases of focal infection, four arteriovenous fistulas, one kinking of an artery, and five perioperatively severed accessory arteries. We conclude that a color Doppler energy evaluation of perfusion differences can be used to detect pathologic lesions in a transplanted kidney.