Introduction: Osseous tissue developes via either endochondral (EC) or intramemberanous (IM) ossification. The bone matrix gelatin (BMG) from both developmental types can induce bone formation when implanted in the muscle of the rat. In this research, the resorption of IM-BMG particles, inductivity of IM-BMG and the nature of heterotropic calcification was evaluated at implantation site. Materials and Methods: The frontal bones from (60) male Spargue Dawely rat (4-8 weeds old) were removed, cleaned, crushed to small chips and used to prepare BMG according to Urist et al, and 2 mg of BMG was implanted in the rectus abdominis muscles of the experimental group, while the control group received a denatured BMG. After 7, 10, 25 and 35 days of implantation, the implants were removed and processed for light and electron microscopes. Results: The inductive capacity of IM-BMG is lesser than EC-BMG, the resoption of IM-BMG is longer than EC-BMG. The acellular mineral deposite (AMD) was reported only in EC-BMG, while AMD was also noticed in this study with IM-BMG.\par Conclusion: The conclusion of this study was that both EC-BMG and IM-BMG have similar bone inducing factors for heterotropic calcification in the implantation site. The resoption of implant is longer in IM-BMG than EC-BMG, but the factors which are involved in the resoption rate are similar.