366 human staphylococci were tested for the production of coagulase and thermonuclease and were subdivided into lyogroups. 98% of the isolates showed uniformly positive or uniformly negative results for the production of two enzymes. All uniformly positive strains belonged to the species Staphylococcus aureus, whereas coagulase-thermonuclease negative strains were easily subdivided into five lyogroups. Seven strains produced only one of two enzymes and were identified by analysis of their bacteriolytic activity. Two of these strains were identified as Staphylococcus aureus, one was coagulase negative and the other thermonuclease negative
