Reconstruction of bone defects and contour irregularities in the craniofacial region is difficult and often requires complex solutions. This study investigated the tissue response, vascularization and bone ingrowth, in hydroxyapatite, porous polyethylene and silicone elastomer when used as bone graft substitutes. 24 albino rabbits (8 rabbits for each implant) were used in this investigation. Hydroxyapatite 500 particles, silicone rubber and porous high-density polyethylene were placed in the cavities formed with a drill in the rabbit frontal bones. As a part of a prospective study the vascularization rates of all implant materials were analyzed 10 days and 2 months after surgery using 99m Technetium-MDP (Methylene diphosphonate) scintigraphy of the skull. The scintigraphic studies were performed 2 hours after intravenous injection of 4 mCi (148 MBq) 99m Tc-MDP. The frontal bone was excised on the 10th and 60th days. All tissue specimens were placed first in 10% formalin and then in 10% nitric acid solution for decalcification. The vascularization, connective tissue ingrowth, foreign body reaction and bone regeneration around the implant were evaluated. Results of this study suggested that hydroxyapatite and porous polyethylene were stabilized in bone while as expected silicone was mobile, also hydroxyapatite implants are vascularized better and are more biocompatible than porous polyethylene.