Background: Diabetes mellitus DM is a systemic metabolic disease. It is characterized by increase blood glucose level over a prolonged period of time. Diabetes is due to either the pancreas is not producing enough insulin, or the cells of the body are not responding properly to the insulin produced.The Aim of the work: To measure the effect of diabetes type-II on corneal endothelial cells using specular microscopy versus normal individuals.Patients and Methods: This is a case-control study including 96-eye of 48-diabetic patients’ type-II from those attending the outpatient clinics of memorial institute of ophthalmology and Helwan University.Results: The results of the current study revealed that the diabetes mellitus may have some adverse effects on corneal endothelial cell parameters. We have found that Specular microscopy is the only investigative tool that measures all corneal endothelial parameters together CCT, CD, CV, HEX.Conclusion: The current study revealed that diabetes mellitus may have an adverse effect on different corneal endothelial cell parameters especially on cell density.