The vitamin requirements of 66 strains of Staphylococcus cohnii from various sources were determined using solidified and liquid chemically defined media. All the strains tested required nicotinic acid and thiamine. Biotin was either growth stimulatory or essential for 34 strains. Pantothenic acid was required by 21 of the 30 strains of known human origin but was not required by any of the 24 strains of murine origin. There was an association among Staph. cohnii strains to grow in the absence of pantothenic acid and biotin and the ability to produce acid from lactose and the possession of phosphatase activity (20 strains). The majority of strains requiring pantothenic acid and biotin were unable to ferment lactose and did not possess phosphatase activity (22 strains).