Primary biliary cholangitis (PBC), formerly known as primary biliary cirrhosis, is an organ-specific autoimmune disease that predominantly affects middle-aged women and is characterized by the chronic progressive destruction of small intrahepatic bile ducts with portal inflammation and, ultimately, fibrosis. The serological hallmark of PBC is the presence of anti-mitochondrial autoantibodies (AMA). Several mechanisms have been proposed for immune-mediated bile duct damage in PBC, including the roles of T cells, B cells, other cell phenotypes, and AMA. A sign of fragility of biliary epithelial cells caused by apoptosis, senescence, and autophagy has also been noted. Several complex steps and mechanisms appear to be involved in the induction and progression of cholangitis and biliary degeneration in patients with PBC. J. Med. Invest. 64: 7-13, February, 2017.