Alpha-1-antitrypsin (AAT) immunoreactive inclusions were found in an adenocarcinoma of a gall bladder of a patient with Pi SZ phenotype who also had globular AAT accumulation in the liver. The inclusions did not react with antibodies against other plasma proteins, thus suggesting a primary synthesis of AAT in these cells. The presence of AAT in the tumor cells may represent resurgence of an oncofetal antigen, or, indirectly, may mean that AAT-containing cells normally exist in the human non-neoplastic gall bladder. The accumulation of AAT in tumor cells might be a basic process in malignant transformation.