Three methods employed to distinguish staphylococci from micrococci were compared, using clinical and environmental strains. When these methods are used, misinterpretation of results, as well as erratic results, may occur, and suggestions for eliminating these problems are provided. The most sensitive test that combines ease of use and speed in obtaining results for distinguishing the two genera is the lysostaphin susceptibility test. Two other tests, facultatively anaerobic growth in semisolid thioglycolate agar and fermentation of dextrose, may also be used to distinguish these two genera, but results are often slow in developing, are subject to technical difficulties, and may lead to incorrect assignment of certain species of staphylococci and micrococci to their proper genera.