This study was performed to evaluate the histopathologic changes of the rabbit tibial compact bone using internal irrigation with both cold and room - temperature saline on drilling. The medial surface of the rabbit tibia was drilled with specially designed pilot drill (2.0mm in diameter) at 300 rpm. When drilling, two different temperature salines were injected (experimental group I : $4^{circ}C$ saline, experimental goup Ⅱ : room - temperature saline). And the control group was drilled without cooling agent. The three rabbits in each two experimental and control groups were sacrificed 1, 2, 4, and 8 weeks after. The bone tissues including the bony defects were fixed with 10% neurtal buffered formalin, decalcified with formic acid, embedded in paraplast, and sterile sectioned at 5-6${mu}m$. And then tissue specimens were stained with H - E and observed under light microscope. The results were as follow : The experimental groups showed early bone repair than the control group at all intervals. They underwent the same course of bone repair until 4 weeks. But the experimental group I showed slightly better bone maturation than the experimental group Ⅱ at 8 weeks.