Unlike most organs, the liver is dually supplied by both arterial and venous blood and contains its own specialized capillary network, the sinusoids. This complex vascular situation means there is a wide array of pathology that can occur in the liver. Portal venous inflow abnormalities can result from the occlusion of large or small portal veins and produce an array of histological findings, including obliterative portal venopathy, hepatoportal sclerosis, and nodular regenerative hyperplasia. Sinusoidal dilatation is a common, nonspecific finding in liver biopsies, but generates a wide differential of occlusive, thrombotic, and toxic causes of sinusoidal injury. Similarly, while hepatic venous outflow impairment presents a fairly straightforward histological pattern, the mechanisms of injury prove much more diverse than simply mechanical obstruction. Even more than with other medical liver evaluations, assessment of vascular pathology of the liver requires careful integration of histopathologic and clinical findings.