Sera from NOD mice were studied for the presence of bovine serum albumin (BSA) antibodies using an ELISA assay. NOD mice had higher levels of BSA binding and higher frequencies of BSA antibodies than did control mice. Furthermore, diabetic NOD mice had higher BSA binding, and higher frequencies of BSA Ab than did nondiabetic NOD mice. These findings are indicative of an exaggerated immune response in NOD mice to BSA that may be associated with diabetes.