To obtain monoclonal antibodies (MAbs) that distinguish secretor and nonsecretor from their saliva in forensic casework, two (K7405 and K7422) and one (K7516) MAbs reacting to blood group A antigen were produced by immunization of mice with salivary mucin obtained from blood group A secretors and nonsecretors, respectively. K7405, produced by immunization with salivary mucin obtained from A secretor, reacted with the A substances bound to the carrier protein but not with the A substance separated from the carrier protein. On the other hand, the K7422 and K7516 were reactive to the A substance separated from carrier protein. From these results, we conclude that K7405 recognizes the A substances clustered on the carrier protein and K7422 and K7516 recognize the isolated A substance. In the forensic blood typing of body fluids, A secretors and A nonsecretors can be clearly discriminated by the combined application of two MAbs (K7405 and K7516), which react differently against saliva samples.