Introduction: Considering the Diabetes mellitus (DM) as one of the oldest conditions characterized in humans, it has been recognized since antiquity and considered as a major health problem at present. There is a need for efficient treatment. Aim: The aim of the present investigation was to find out whether statins can alleviate the well documented side effects of Streptozotocin induced diabetes mellitus on the periodontal ligament of adult male Albino rats. Material and Methods: Sixty adult male albino rats with body weight ranging from180-200gr were used in this investigation. They were divided into the following groups. Group 1: consisted of 20 animals and served as controls. Group 2: consisted of 20 animals, they were subjected to a single intraperitoneal injection of streptozotocin in a dose 60 mg/kg body weight
of for induction of diabetes mellitus. Group 3: consisted of 20 animals. They were subjected to induction of diabetes mellitus in the same way as group 2 animals. One week later, the animals were treated with simvastatin in a daily intraperitoneal dose of 5mg/kg body weight. At the end of the experiment the animals were sacrificed by cervical dislocation, their Jaws were dissected out then processed for the histological and transmission electron microscopic examinations. Results: The present work showed that the treatment of diabetic rats with statins resulted in amelioration of the degenerative effect of diabetes on the periodontal ligament when compared with. Changes of diabetes in group 2 and regenerative changes of statins in group 3 compared to the control group 1. Conclusion: Diabetic albino rats treated with statins revealed partial improvements, mostly in the arrangement of the fibers of periodontal ligament.