Tc-99m-HIDA, like bilirubin, is an organic anion that accumulates in hepatocytes, is secreted into the bile canaliculi and excreted in bile. It is therefore used to image hepatobiliary disease. The most frequent indication is biliary dyskinesia, which comprises cystic duct syndrome, sphincter of Oddi dysfunction and hyper-responsive gallbladder. In hospitals with specialist liver units, patients are referred with suspected obstruction at biliary anastomoses, bile leaks and for the monitoring of differential function between native liver and auxiliary transplants for acute liver failure. Paediatric indications include biliary atresia, neonatal hepatitis and choledochal cysts. It is important to recognise obstruction as a separate entity from intrahepatic cholestasis in which tracer fails to be transported from hepatocyte to bile canaliculus - from cholangiopathy or drugs - and returns to sinusoidal blood.