Color Doppler sonography is an important noninvasive diagnostic tool for detecting abnormalities of the hepatic vasculature in patients with diffuse liver disease. To study its usefulness in these cases, we retrospectively reviewed the findings in 147 patients with abnormal portal venous color Doppler sonograms. This group comprised all patients with abnormal portal venous color Doppler sonograms studied from February 1987 to July 1989. Correlative imaging was not available in all cases. The sonographic diagnoses included (1) portal venous thrombosis (50 patients, 93 vessels); (2) portal-systemic or portal-portal collaterals (80 patients, 95 collaterals); (3) reversed, bidirectional, or other abnormal portal venous flow patterns (36 patients); and (4) abnormal hepatic arterial flow (20 patients). Since the results reported derive from a retrospective review without consistent correlation with other imaging studies, no appraisal of the sensitivity or accuracy of portal color Doppler sonography could be made from our data. The ability of color Doppler sonography to visualize flow without altering hemodynamics has led to several novel observations in these patients. These include increased arterial flow in states of low portal blood flow, reversal of portal flow direction postprandially, coincident reversed and hepatopetal flow in different branches of a single portal vein, and normal helical portal venous flow. These and other findings show that color Doppler sonography has enhanced our ability to detect abnormalities of the hepatic and portal venous system.