Diabetes mellitus is a hyperglycemic clinical manifestation due to a dysfunction of metabolic systems (carbohydrate, lipid and protein metabolism) and is one of the most common disorders of endocrine. It is usually recognized as a result of the abnormal secretion of insulin by pancreatic ?-cells, inability of the insulin to stimulate the peripheral utilization (muscles and adipocytes) and increased endogenous glucose production by liver. DM is classified as Type 1 and Type 2 diabetes. The cause of the Type 1 diabetes mellitus has been attributed to lower insulin level in the body due to autoimmune destruction of ?-cells. Alterations in male reproductive system have been widely reported in diabetic human and also in model animals with diabetes.This book focuses on the alloxan induced diabetes on male reproductive hormones and testicular histology in male rabbits. This book demonstrates the effects of diabetes on animal reproductive system; and will add new research and knowledge to the hazardous effects of diabetes that it contributes to the male rabbits.