INTRODUCTION:Ozone (O3) gas is a molecule consisting of three atoms of oxygen in a dynamically unstable structure due to the presence of mesomeric states. Ozone therapy has been utilized and heavily studied for more than a century. Its effects on bone are proven and consistent. It enhance osteoblastic activity and new bone formation. Diabetes mellitus (DM) is a chronic metabolic disease that potentially affect bone metabolism, structure, and mineral density. OBJECTIVES: to evaluate histologically the possible effect of ozone therapy on bone healing after tooth extraction in rabbits with alloxan induced diabetes mellitus. MATERIALS AND METHODS Thirty adult male New Zealand rabbits weighing 1500-2500 grams (approximately six months of age) will be divided into 3 equal groups: group I;(control group), group II; (diabetic group): diabetes was induced by a single intravenous injection of alloxan in a dose of 100 mg/kg and group III:(Ozone group) rabbits was treated as in diabetic group then they was treated with ozone therapy which will be applied topically in the form of gel inside the tooth socket. Rabbits were sacrificed after six weeks. Each sample were dissected and prepared for histological evaluation. RESULTS: in diabetic group the socket showed empty central region surrounded by disorganization bony trabeculae. The bony trabeculae surrounded less vascular spaces and more fibrous tissue.in diabetic group treated with ozone therapy the socket showed complete filling of the socket with newly formed bone.The socket with newly formed bone surrounding highly vascular bone marrow. CONCLUSIONS: Ozone gel application accelerates socket healing and enhances bone formation in diabetes mellitus