Summary.After freeze‐etching, cells ofMicrococcus denitrificansandM. halodenitrificansrevealed structures similar to those observed in ultrathin sections. Both organisms had a similar cell wall structure. The cell wall was double layered, the smooth surface of which had a delicate granular structure. The cytoplasmic membrane was in 2 parts, both covered with spherical particles 8–12 nm diam. The cytoplasmic membrane possessed rod‐shaped invaginations (100–300 × 30–50 nm). The cytoplasm of both species contained inclusions of poly‐β‐hydr