Congenital absence of the portal vein (CAPV) is an unusual condition that often is associated with other anomalies. This is the first report of reduced-size liver transplant in a patient with CAPV. Because the presence of this rare congenital portasystemic shunt, there was no portal-systemic pressure differential, and thus an absence of collateral vessels in the pretransplant state. As a result, surgery was complicated by severe mesenteric edema caused by an increase in portal pressure when the allograft was implanted. The morbidity associated with CAPV usually results from associated conditions, but if transplantation is necessary, careful management of mesenteric congestion is crucial to success. The authors' experience and a review of the literature indicate that the CAPV can be classified into one of two groups of portasystemic anomalies.