Two morphologically identical strains ofCephalosporium chrysogenum were compared with respect to physiological and biochemical properties. Similar patterns of carbohydrate and hydrocarbon utilization were noted for both strains. Each strain was enzymatically active against the following substrates: beef fat, arbutin, urea, casein, lignin, and cellulose. A yellow pigment was produced by both strains in various agar media. Vitamins were not essential for growth. Each organism could be cultivated in the presence of 40% glucose. Both strains yielded antibiotics inhibiting the growth of gram-positive and gram-negative bacteria. Chromatography of cell hydrolysates of theC. chrysogenum strains revealed the presence of ribose, glucose and galactose.