The blood supply to the gallbladder is through the cystic artery (17), which usually arises from the right hepatic artery (18). In the triangular zone bounded by the cystic duct joining the common hepatic duct and the cystic artery, Calot's triangle, there are more anatomic variations than are found in any other location. The most common variations in this zone, which is no larger than 3 cm in diameter, are related to the origin of the cystic artery. It most commonly arises from the right hepatic artery (18) after the latter vessel has passed beneath the common hepatic duct. The cystic artery may arise from the right hepatic artery more proximally and lie anterior to the common hepatic duct. Other common variations include origin of the cystic artery from the left hepatic artery (19), the common hepatic artery (8), or the gastroduodenal artery (10); additionally, these cystic arteries may have uncommon relationships to the biliary ductal system. The variations in the hepatoduodenal ligament are so numerous that nothing should be ligated or incised in this area until definite identification has been made.