To evaluate the effect of acute viral hepatitis on hepatic arterial blood flow, we performed color Doppler sonography with point-spectral analysis in 15 patients with acute viral hepatitis and compared the results with those in 15 normal volunteers. During the acute phase of hepatitis, the peak-systolic and end-diastolic velocity of the hepatic artery were significantly larger than those in normal arteries (p < 0.01). During the recovery phase, these indexes of the hepatic artery decreased significantly to the control levels (p < 0.01). The resistive indexes related to vascular resistance in the hepatic artery during the acute phase were significantly less than those in normal arteries (p < 0.01), and they increased significantly to the control levels during the recovery phase (p < 0.01). No significant correlation was found between these indexes of the hepatic artery and conventional liver function parameters. However, the interval between the acute phase and the recovery phase did correlate negatively with the peak-systolic velocity of the hepatic artery in the acute phase (r = -0.630, p < 0.05) and with the end-diastolic velocity (r = -0.514, p < 0.05). We conclude that color Doppler sonography is useful for imaging increased hepatic arterial blood flow in patients with acute viral hepatitis. We believe that increased hepatic arterial blood flow during the acute phase may provide a marker for earlier recovery from hepatitis-induced damage.