Abstract: Disclosed herein is a monoclonal antibody of the IgM class which reacts with a glycoprotein antigen having a molecular weight by gel filtration of 1,000,000 or higher, the antigenic determinant to be recognized being a sugar chain with a sialic acid residue at the end thereof. The monoclonal antibody has the following characteristics: (1) a reactivity with human cancers of stomach, large intestine, pancreas, breast, lung, biliary duct, uterus and esophagus; (2) a reactivity with normal human submaxillary gland, proximal renal tubule, bronchial gland, squamous epithelial corneum, pancreatic Langerhans' islands, liver cell membrane and duodenal gland; (3) a reactivity with human intestinal metaplastic gastric mucosa; and (4) a non-reactivity with normal human prostate gland, biliary duct and pancreatic duct.Also provided in the invention is a method for production of monoclonal antibodies.