The ability of mitochondria and immune cells to oxidize the substates of the glutamine family amino acids has been studied. It was shown that brain mitochondria in the state 3 of respiratory chain oxidizes glutamine, glutamate and GABA+a-ketoglutarate with same rate, which however is much less than that of succinate. The thymocytes oxidizes amino acides substrates with much less intensity. In splenocytes even succinate the better respiratory substrate doesn't stimulate the oxygen consumption in appreciably extent and ATP or ADP addition to incubation media inhibits respiration of the thymocytes and particularly in splenocytes. The low rate of glutamine oxidation in immune cells doesn't agree with the high rate of glutamine hydrolysis in these cells.