Purified disaccharide peptide monomers obtained from Neisseria gonorrhoeae by enzymatic digestion of gonococcal peptidoglycan damaged the mucosa of human fallopian tubes in organ culture. Two peptidoglycan fragments were tested: a nonreducing, anhydromuramyl-containing monomer (the principal fragment shed by growing gonococci) and the analogous reducing, muramidase-derived monomer. The damage produced by either of these peptidoglycan monomers resulted in sloughing of ciliated cells from the mucosa and resembled the damage observed in active gonococcal infection and that produced by filter-sterilized toxic supernatant fluids from gonococcal-infected organ cultures. The minimal toxic dose of peptidoglycan monomers was 0.75 micrograms/ml. Neither lipopolysaccharide, sodium dodecyl sulfate, nor Triton X-100, possible contaminants from the monomer-purification procedures, was present in sufficient quantity to account for the damage. Both of the gonococcal peptidoglycan monomers may be present in vivo and thus may play a role in the pathogenesis of gonococcal infection.