N. meningitidis strains isolated from 218 healthy carriers in 1989-1991 in closed communities of adults, irrespective of cases of meningococcal infection registered in these communities, were characterized with a variety of different type and subtype antigens. Only in 139 strains (63.76%) their types and/or subtypes could be determined with the use of a set of 6 serotypes and 11 subtypes of monoclonal antibodies. 26 group B strains and 31 group C strains had multiple antigenic composition. 13 group A strains were found to be more homogeneous: 8 of them, isolated in one area, belonged, according to Dr. Achtman's data, to a definite clone VI-1, heretofore unknown. No prevailing serotype/subtype could be revealed, which reflected the wide heterogeneity of N. meningitidis at the period of the decrease of morbidity in meningococcal infection. The observed stability of serotype/subtype of strains, isolated from the same carriers and circulating in the same communities, suggests that the serotype/subtype of N. meningitidis is a valuable epidemiological marker.