Intra‐arterial digital subtraction angiography (IA‐DSA) is used in gastrointestinal (GI) angiography. This chapter reviews the equipment and technique used in catheterization of the visceral arteries and portal venous system, vascular anatomy, and the role of angiography in the diagnosis and treatment of visceral vascular and GI diseases. The combination of wedged hepatic venography and manometry with transjugular liver biopsy provides information on hepatic‐portal anatomy, hepatic hemodynamics, and liver histology. Blood flow direction in the intrahepatic and extrahepatic portal veins can be assessed by Doppler ultrasound, transhepatic portal vein catheterization, superior mesenteric and celiac angiography, and wedged hepatic venography. CT and MRI are the primary imaging methods used for the diagnosis of hepatocellular carcinoma (HCC). Transcatheter embolotherapy is an acceptable alternative to surgery in treating massive arterial GI bleeding, visceral aneurysms and pseudoaneurysms, hypersplenism, isolated gastric varices associated with splenic vein occlusion, and traumatic hepatic and splenic bleeding.