An experimental comparative study on bone formation regarding surface implantation was performed on thirty three adult mongrel dogs; using either a hydroxyapatite soaked in sodium fluoride (F-HAP) or a hydroxyapatite (HAP). F-HAP was made as follows: the HAP was soaked in 100ml of sodium fluoride solution of 5ppm., 10ppm. and 100ppm. concentration for an hour under vacuum deaeration+. Under general anesthesia, specimens were implanted into the bone immediately inferior to tibial tubercle by opening a window using a 3.5mm drill. Postoperative course was observed periodically (radiologically, macroscopically and histopathologically) from one to twelve weeks. There were no marked differences on X-rays or macroscopic findings between HAP and F-HAP. Histopathologically, there was significant new bone formation in the F-HAP specimens up until four weeks postoperatively. The 5ppm specimen especially indicated the most significant bone formation. The results of this study suggested that F-HAP was a better biomaterial (concerning new bone formation on the implant's surface) and that 5ppm was at optimal concentration for early new bone formation.