The catabolic pathways for the utilization of glucose and gluconate in one representation of each of five species of Arthrobacter were studied by the respirometric method (Wang et al. 1958). The results indicate that these Arthrobacter organisms can be classified into two groups on the basis of their catabolic behavior. The first group (Arthrobacter ureafaciens, A. globiformis) relies primarily on the operation of the Embden-Meyerhof-Parnas pathway and to some extent the hexose monophosphate pathway for the assimilation of glucose. In the second group (A. simplex, A. pascens, A. atrocyaneus)glucose is catabolized primarily by way of the intermediary formation of gluconate; the Entner-Doudoroff and the hexose monophosphate pathways appear to be the major routes for the assimilation of glucose and gluconate.