A hamster serum protein which reacted with anti-human pancreatic oncofetal antigen (POA) was identified in sera from hamsters with varying types of pancreatic pathology. Hamsters were treated with N-nitrobis-(2-hydroxypropyl)-amine, and histological findings in the pancreas were correlated with hamster POA. The cross reactivity of anti-human POA with hamster POA was poor. As a result, the sensitivity of this assay was too low to permit its use in serologically discriminating carcinogen-induced pancreatic cancer from other pancreatic pathologies. A specific antiserum and assay system to hamster POA may overcome this problem.