SUMMARY: The glycerophospho-compound which has been shown to account for more than one-quarter of the total organic phosphate of Micrococcus pyogenes is present almost exclusively in the particulate fractions of mechanically disintegrated cell suspensions. The main particulate fraction corresponds to the cell envelope material of Dawson (1949). Three-quarters of the weight of this material is made up of a glycerophospho-protein complex of which the protein moiety resembles silk fibrom in amino-acid composition and in its general properties. The amount of hydroxylamino-acid in the protein of the envelope would be sufficient to bind the polyolphosphoric acids covalently, but the possibility that the polyolphosphoric acids form a polymer which is adsorbed on to a protein matrix is not excluded. A subsidiary particulate fraction, made up of very small particles containing a high proportion of phospholipid, was found to be otherwise similar in composition to the envelope fraction. It is suggested that in the intact cell, the material of the small particle fraction may form a continuous layer (lipid membrane?) lying beneath the glycerophospho-protein complex envelope (cell wall?).