A human carcinoembryonic antigen (CEA)-producing cell line, T3M-4, has been established from explant cultures of a primary human pancreatic exocrine adenocarcinoma transplanted into nude mice. The tumor had metastasized in the patient. The tumor obtained from metastatic lymph nodes was the initial source for implantation in athymic nude mice. In the primary culture, host fibroblasts were eliminated by the use of the antiserum raised against nude mouse cells. T3M-4 cells have been continuously propagated in vitro during the past 26 months. The cells grew in a monolayered sheet with about 31 hours of population doubling time. The cells exhibited epithelial morphologic features resembling the structure of the original tumor, and they showed tumor takes when inoculated into athymic nude mice. Xenografts established from the cell line have retained a similar histology to the original tumor on serial transplantation. Chromosomal analysis revealed the cell line to be a human aneuploid one with a hyperdiploid mode. T3M-4 cells possess the characteristic function of CEA secretion in vitro in culture and in vivo in nude mice bearing the tumors produced by inoculation with the cultured cells. In view of these characteristics, T3M-4 cell line represents a new human pancreatic exocrine adenocarcinoma cell line that produces CEA.