Forty strains of micrococci representing all the 8 biochemical types of Baird-Parker (4) were examined for their content of bacterial agglutinogens and antigens sensitizing normal and tanned sheep erythrocytes. Special attention was paid to the urinary pathogens of type 3. Agglutination of the strains in 10 rabbit immune sera against all biochemical types, before and after absorption, showed that the Micrococcus strains have a number of agglutinogens without any systematic pattern. The majority of the agglutinogens are shared by many strains, irrespective of biochemical type. Agglutinogens characteristic of the biochemical types were not demonstrated. Strains of the same biochemical type were, as a rule, not more related antigenically than strains of different types. The indirect haemagglutinations revealed that the micrococci have several shared antigens sensitizing normal and tanned sheep erythrocytes to agglutination in Micrococcus and Staphylococcus aureus immune sera.