A method is suggested for preparing ultra-fine sections of free phage particles. After adding antiphage serum and OsO₄ to the phagofiltrate the material is lyophilized in a frozen state. Later the material is placed into a metacrylate mixture with benzoyl peroxide, and is afterwards embedded by the usual method. Preliminary data are presented on the electron microscopic picture of phage particles (the ultra-fine sections).