Doppler color flow imaging has been used to identify obstruction, rejection, and nonfunctioning renal allografts. When done in the immediate posttransplant period on poorly functioning kidneys, it allows early and accurate detection of surgically correctable changes such as arterial or venous thrombosis or early obstruction by blood, urine, or lymph. Further, it determines changes in intrarenal flow patterns that may indicate early transplant dysfunction, such as acute tubular necrosis and/or acute rejection as well as obstruction. Additionally, baseline values can be obtained in uncomplicated cases for serial follow-up. Between July 1980 and February 1991, 20 transplant patients had Doppler color flow imaging in the immediate posttransplant period. The kidney contour, perirenal collections, vessel flow patterns, and resistive indexes were assessed. In two patients, immediate surgical intervention salvaged the allograft. In several other patients with primary nonfunctioning kidneys, the study distinguished between acute tubular necrosis and obstruction due to external compression. We concluded that protocol Doppler color flow imaging is valuable in the immediate posttransplant period for determining surgically correctable complications.