Periportal contrast enhancement relative to adjacent liver and portal blood has been reported on CT scans in cases of schistosomiasis and hepatic Kaposi sarcoma in AIDS patients. We observed this phenomenon in 10 (8%) of 130 consecutive, contrast-enhanced, nondynamic CT examinations of the abdomen. Thus, the occurrence is more common and less specific than previously reported. Seven of the 10 patients in our series were receiving chemotherapy for malignant disease, and three had abdominal pain with no definitive diagnosis. In four of the 10 patients, corresponding areas of periportal low attenuation or radiolucency were observed on initial dynamically enhanced scans. Periportal enhancement may be related to late diffusion of contrast material into periportal areas that were initially radiolucent. Such diffusion may occur because of endothelial insult. Periportal contrast enhancement appears to be a nonspecific finding on nondynamic contrast-enhanced CT scans of the abdomen. Periportal enhancement is important to recognize because it can mimic the appearance of portal vein thrombosis and may also be used to differentiate intrahepatic biliary dilatation from periportal radiolucency.