Abstract: Structure of inclusions in isotropic pitch-based graphite fibers have been investigated by using TEM. The longitudinal sections of most inclusions are shoe-shaped, ellipsoidal or circular. These inclusions have layer structure which consists of a number of flaky crystallites. Theses flaky crystallites are parallel to each other and perpendicular to the fiber axis. Fissures which are perpendicular to the fiber axis have been found inside the inclusion.