The enhancement characteristics of the liver, aorta, and hepatic vein were evaluated during computed tomography with arterial portography (CTAP) performed with spiral technique in 10 patients. The attenuation of the liver was nearly constant over the scanning interval (average attenuation, 168 HU +/- 16). The attenuation of the aorta increased by an average of 54 HU +/- 31, and the average attenuation of the hepatic vein was 250 HU +/- 34. These data indicate that high levels of liver parenchymal and vascular enhancement can be reliably obtained with CTAP performed with spiral technique.