Plasmids 1.6, 2.8, or greater than 40 megadaltons in size were found in one urethral and nine throat strains of meningococci. Throat meningococci are known to be heterogeneous in their aminopeptidase profiles. Their unexpected content of plasmids is further evidence of their difference from classic systemic strains. Although the 2.8 megadalton plasmid has some resemblance to the well known 2.6 megadalton gonococcal plasmid, restriction enzyme studies gave no evidence of identity. Possible sources of the plasmids are discussed.