To elucidate intramembranous bone reactions to tantalum bone markers, 0.8-mm tantalum balls were implanted in the craniofacial region of 9 male New Zealand white rabbits. After 1, 2, 4 and 16 weeks the animals were sacrificed for SEM. Implant stability for these intervals was controlled by roentgen stereophotogrammetry. Fibrocytes and deposed fibers were seen to immediately adhere to the ball surface, getting retention in its porosities. A successively increasing bony support was observed to have intimate junctions without intervening fibers or soft tissues. No apparent differences in bone reactions were seen between the neurocranial and splanchnocranial bones. Osseointegration confirmed the inertness of tantalum to bone tissue and strongly confirms its suitability for implantation in bone.