From a total of 40 characters that were previously used to differentiate species of staphylococci, 13 key characters were selected to make a simplified scheme that could be easily used by the routine clinical laboratory for identifying human staphylococci. These key characters included coagulase activity, hemolysis, nitrate reduction, and aerobic acid production from fructose, xylose, arabinose, ribose, maltose, lactose, sucrose, trehalose, mannitol, and xylitol. In the simplified scheme, 924 strains of staphylococci were placed into 11 positions, each of which contained the major portion (greater than or equal to 80%) of strains of one of the recognized species. Several positions contained a rare or few uncommon strains of one or more additional species and these could be resolved on the basis of other key characters.