The phenotypical similarity between 34 microbial strains was determined, and they were classified on the principle of maximal general similarity in 70 traits. All the strains were subdivided into three groups within which the similarity of the strains was not less than 85%. The groups correspond to the species Mycococcus capsulatus, M. ruber, and Mycobacterium brevicale. The results of the investigation suggest that the group of mycococci possesses a considerable number of characteristics which make it possible to consider it as a separate microbial genus. However, the principle of equal weight can be hardly applied to the taxonomy of mycococci since sharp variations in many traits do not permit to differentiate between specific and strain differences. Morphological and cultural properties still remain the most reliable criteria of the genus Mycococcus.