The catabolism of pyruvate and acetate in selectedNeisseriaspecies was studied by radio‐respirometry. Both substrates were oxidized via the tricarboxylic acid cycle.N. elongataand the “false neisserias” (N. catarrhalis, N. ovisandN. caviae) did oxidize acetate in the absence of other substrates. This can be explained if it is assumed that these species have glyoxylic acid cycle activity. In the “true neisserias” other thanN. elongata, acetate was oxidized only in the presence of glutamate, indicating that these species do not possess a glyoxylic a