A hepatic artery coursing within the portacaval space was seen in 30 (18.3%) of 164 consecutive patients in whom this region was seen with ultrasonography. In 12 subjects (40%) this vessel represented the right hepatic artery arising from the proximal celiac artery. In the other 18 subjects (60%) this vessel arose from the superior mesenteric artery. It should not be assumed that a hepatic artery traversing the portacaval space arises from the superior mesenteric artery until its origin is clearly documented.