Carcinoma of the pancreas, especially the tail or body, is difficult to detect and diagnosis is almost always too late. The reason for this is the inaccessibility of the pancreas to physical and radiological examination as well. A specific biochemical or serological test would improve early diagnosis and ultimate survival rate of this catastrophic disease. It has been shown that a specific antigen (oncofetoprotein) can be prepared from fetal pancreas and pancreatic cancer tumors. This oncofetal antigen was found in the sera of 37 of 38 patients with carcinoma of the pancreas but absent from healthy controls as well as patients with diseases other than carcinoma of the pancreas. Antisera to this pancreatic oncofetoprotein will be raised in rabbits by immunization with extracts of fetal pancreas and pancreatic cancer tumors. After evaluation of the antisera, pancreatic carcinoma patients' sera will be tested for the presence of this oncofetoprotein initially by the double-diffusion technique and later on by more sensitive methods such as counterimmunoelectrophoresis and radioimmunoassay. Spontaneous antibodies and anti-antibodies will be sought in the sera of patients with carcinoma of the pancreas, and their blocking or unblocking effect of cell-mediated anti-tumor immune reactions will be studied.