A rare case of rectal carcinoma with a high serum alpha-fetoprotein (AFP) level (maximum, 6,983 ng/ml) is reported. The histology of the primary tumor was adenosquamous carcinoma, the major component being moderately to poorly differentiated adenocarcinoma. Immunohistochemically, a few AFP-positive cells were identified in the primary tumor. However, numerous AFP-positive cells were observed in metastatic tumors in the liver and lungs at autopsy, which were histologically undifferentiated carcinoma with marked pleomorphism. Furthermore, components of adenocarcinoma were present in the metastatic tumors at various sites, and components of squamous cell carcinoma were seen only in the pelvic cavity. To our knowledge, this is the first case of rectal carcinoma with verified AFP production by the tumor cells.