As a result of the study of a number of additional characteristics, more than a half of the cultures, formerly identified as phosphatase-negative S. epidermidis according to the scheme of the International Subcommittee on the Taxonomy of Staphylococci and Micrococci, have been shown to be more similar to S. Hominis and S. captis on account of their properties. The study of correlation between the main differentiating characteristics of S. epidermidis has shown that it is poorly pronounced. For this reason the decision to classify a phosphatase-negative culture with S. epidermidis should be based on the study of additional characteristics which differentiate this species not only from S. saprophyticus, but also from other phosphatase-negative staphylococci.