1. The utilization of various organic acids as sole source of carbon by M. glutamicus was studied. Organic acids examined are classified into three groups, namely (1) those which can be assimilated when the media contain biotin as sole growth factor, (2) those which can be assimilated when some auxiliary nutrients are added besides biotin, and (3) those which can not be utilized at all by the organism even with added auxiliary nutrients.2. The culture conditions for the L-glutamic acid production from acetate were also studied. It was observed that a considerable amount of L-glutamic acid was produced in a medium having biotin as sole growth factor.3. The culture conditions for the L-glutamic acid production from citrate were studied. An appreciable amount of L-glutamic acid was produced in a medium containing biotin and corn steep liquor.4. Relationship between the concentration of biotin in the medium and the L-glutamic acid production was shown to be similar to the case of L-glutamic acid production from glucose.5. Metabolic activities of the cells grown on glucose, citrate and acetate were studied. The yield of L-glutamic acid by these cells is discussed in correlation with oxidation of the substrates.