Growth of Neisseria gonorrhoeae strain FA171 in continuous culture under glucose-limiting conditions resulted in a growth-rate-dependent change in the lipopolysaccharide (LPS). The evidence for this change is an alteration in the mobility of purified alkali-treated LPS on sodium dodecyl sulfate-polyacrylamide gels and a quantitative difference in the amount of the LPS serotype antigen. The LPS from cells grown at a low dilution rate (0.12 h-1) contained ca. eightfold less serotype antigen than the LPS from cells grown at a high dilution rate (0.56 h-1). The decrease in LPS serotype antigen was associated with an increase in sensitivity to the bactericidal activity of normal human serum and an increase in cell surface hydrophobicity. An increase in the amount of serotype antigen was associated with a reduction in the accessibility of a monoclonal antibody to a core LPS determinant, an increase in resistance to normal human serum, and a decrease in cell surface hydrophobicity. The microheterogeneity of gonococcal LPS with respect to the content of serotype antigen may result from an alteration in the metabolism of glucose.