Fifty-two strains found to belong to Flavobacterium meningosepticum on the basis of DNA-DNA hybridization analyses were characterized and found to be phenotypically homogeneous. All strains were oxidase, catalase, indole, gelatinase and beta-galactosidase positive, and produced acid from glucose, mannose, fructose, maltose and mannitol; nitrate was not reduced. F. meningosepticum could be differentiated from Flavobacterium group IIb by its ability to produce beta-galactosidase, and by the latter taxon's ability to produce a bright yellow pigment in contrast to the weak or non-existing pigmentation of F. meningosepticum. Phenotypic characteristics that could differentiate between the two main DNA relatedness groups of F. meningosepticum were not discovered, wherefore a subdivision of the present species into two species cannot be recommended. Strains from the DNA relatedness groups comprising 19 of 20 CSF isolates were found to be able to grow at 40 degrees C and to produce a weak yellow pigment; in contrast, strains from the three other DNA relatedness groups were unable to grow at 40 degrees C and produced no pigment.