A new species of gram-positive, aerobic, nonacid-fast bacterium capable of producing large quantities of lipids has been described. Its morphologic and physiologic characteristics place it in the genusCorynebacterium, and the brilliant red color of its colonies has suggested for it the species namerubrum. The new species may be of particular interest to the immunologist, since it seems to have some of the adjuvant activities peculiar to acid-fast bacteria.