In studying the submicroscopic structure of the L-form of streptococcus, group A, isolated from the heart tissue of rabbit there were revealed intracytoplasmic membrane structures. Ring lamellar structures were most frequently revealed in the spheroid cells with dense and loose cytoplasm. They were also found in dense cytoplasm of elementary bodies. Myelin-like structures or those resembling a bundle of microtubules were less incident. Fibrillar structures collected into bands, 64--140 nm in with, and located on one or both sides of the cells beside the cytoplasmic membrane were revealed in the spheroid cells. Individual fibrillae, 8 to 10 nm in diameter, adhered one to another, interlaced, and were sometimes located in parallel. The fibrillar band was loose in the lysed cells.