Riboflavin carrier protein is an essential protein required for the growth and development of the embryo and hence for the maintenance of pregnancy. Our efforts to delineate the antigenic determinants of chicken riboflavin carrier protein (cRCP) resulted in the identification of a bioneutralization epitope in the region 10-24 of cRCP. The present work compares the properties of the antibodies raised against the peptide epitope by classical and multiple antigen peptide (MAP) system approaches. The extent of cross-reaction of the antibodies to the MAP construct with the parent protein was found to be significantly less as compared to the antibodies raised against the peptide-diphtheria toxoid conjugate. Furthermore, the bioneutralizing ability of the antisera to the MAP construct was also found to be very poor. The results suggest that there are serious limitations in the ability of antibodies raised against MAP constructs to cross-react with the native proteins.