Luteinizing hormone releasing hormone (LHRH) has been intensively studied as a target for the control of fertility and hormone dependent cancers. In most studies a decapeptide, EHWSYGLRPG, which is identical to the native LHRH sequence, has been used. In this study we investigated whether short sequences of LHRH could retain immunogenic and antigenic properties and be employed in a vaccine preparation. Our results show that the C-terminal five-residue peptide (LHRH(6-10)) of LHRH was able to inhibit the binding of anti-LHRH(1-10) antisera to LHRH(1-10) in an inhibition ELISA. A totally synthetic peptide vaccine incorporating LHRH(6-10) also elicited a strong anti-LHRH antibody response and prevented mice from becoming pregnant in fertility trials. The primary immune response elicited by a peptide vaccine based on LHRH(1-10) could be boosted with LHRH(6-10). Finally, an antigen system comprising of biotinylated LHRH(6-10) bound to streptavidin-coated plates was capable of discriminating between anti-LHRH antibodies present in fertile and non-fertile mice. This study demonstrates that LHRH(6-10) retains immunogenic and antigenic properties and also discerns antibody specificities associated with reproductive competence.