BACKGROUND AND OBJECTIVE. Although previous studies have provided new information on bone repair, there are still gaps in knowledge about resorptive and formative processes during bone repair at the electron microscopic level. The aim of this study was to compare bone repair after the internal fracture, osteotomy, and bicortical perforation of the tibia by means of electron microscopy. MATERIAL AND METHODS. An electron microscopic study of bone repair after the internal fracture, osteotomy, and bicortical perforation of the tibia was performed on 72 male Wistar rats. Rats undergoing osteotomy and perforation were further subdivided into the control and immobilization subgroups. Bone repair was observed during the first posttraumatic weeks. RESULTS. Although bone repair in general had similar bone healing stages in all the groups, the repair process depended on the mode and degree of injury thus being different in the experimental groups. After the internal fracture, indirect ossification was observed; after osteotomy, primary periosteal, secondary endosteal ossification was noted; and after perforation, primary endosteal, secondary periosteal ossification was documented. Immobilization had an inhibitory effect on bone repair. CONCLUSIONS. The results of the present study gave new information at the electron microscopic level about intracellular changes and intercellular matrix synthesis during different types of posttraumatic bone repair and confirmed our previous reports on similar posttraumatic bone repair in histomorphometric and immunohistochemical studies.