MAb HSA133 stains human liver canaliculi and a subset of hepatocellular carcinomas. In frozen sections, it stains liver canaliculi strongly and may be used as a marker of this hepatic substructure. Cell preparations of hepatocellular carcinoma biopsies and cell lines are found to bind this MAb on the cell surface. HSA133 strongly stains liver canaliculi and hepatic carcinoma cells using frozen sections or paraformaldehyde fixed cell preparations.