Neisseria gonorrhoeae DNA that encodes the pathogenic Neisseria H.8 common antigen was cloned in the lambda phage sep6. The recombinant phage, designated s6H.8, was detected immunologically with a monoclonal antibody that binds to the H.8 antigen. The gonococcal and s6H.8 forms of the antigen yielded identical partial proteolysis epitope maps. Neisseria species that did not manifest the H.8 antigen showed little or no DNA homology with s6H.8. This clone should facilitate investigation into the clinical utility of this antigen and determination of its possible function in gonococcal pathogenesis.