Three strains of' Pseztclonronn,r Migula, capable of utilizing phenol and other aroiriutic cornpounds as sole sonrces of ciarbon, are described. They resenible certain strains of Pa. aeruginosa and E'. f i i w r e s c e m except, in t.his ability.MANY STRAINS of Pseudomonos have been reported to have the ability to attack various aromatic compounds. These have sometimes been referred to Ps. $uorescenes or, though less often, to Ps. aeruginoaa. Sometimes they have been described simply as 'Pseudomonas sp.' and occasionally they have been given tjhe st,atus of new species, but seldom have they been fully characterized.Two cultures of Gram-negative, nonsporing, polar flagellate rods were isolated from solutions of mineral salts to which 0.5 0; of phenol had been added as a preservative and from which it had completely disappeared. Both strains were able to grow for many successive subcultures in a mineral medium with 0.1% of phenol as the sole carbon source, and retained this ability even after prolonged cult>ure in brot'h devoid of phenol. They produced pyocyanin as well as the fluorescent pigment common to many pseudomonads, and thus resembled Ps. aeruginosn (Schrogter) Migula rather than any species particularly chamcterized by the ability to attack aromatic compounds. e.g. Ps. phenoiis Hamdy P t ul. (1956). Further, one of 13 nonpyocyaninogenic cultures of Pseudomoms spp. from various sources, all of which had been maintained in broth for three or more years, was also found to be able to ntilize phenol, and it seemed desirable to compare these cultures with strains of known species of Pseudomoms which did not possess that property. MATERIALS AND METHODSOrganisms. Three phenol decomposing strains were examined. Two of these were the new pyocyaninogenic isolates N 63 and N 63 from the phenolized mineral salts solution, mentioned above, and the third, G 489, was a nonpyocyaninogenic culturc.