Bacillus larvae appears to be unique among related bacilli in that it contains enzymes of the Embden-Meyerhof-Parnas, pentose phosphate, and Entner-Doudoroff pathways. Simultaneous occurrence of enzymes of all three metabolic pathways has not until now been reported in other Bacillus species. Radiorespirometric analyses of specifically labeled glucose catabolism reveal that vegetative cells of B. larvae dissimilate glucose predominately via a direct oxidative route and to a lesser extent by a nonoxidative scheme although specific activities of enzymes of all three pathways are comparable. Predominance of an oxidative pathway is unusual and also has not been reported for other bacilli. Studies on the oxidation of pyruvic, acetic, succinic, and alpha-ketoglutaric acids show that terminal respiration of cells in transition from vegetative growth to sporulation involves both the tricarboxylic acid and glyoxylic acid cycles. The relationship of these findings to the fastidiousness and oligosporogeny of B. larvae is discussed.