Diabetes contributes to neurological dysfunction including peripheral nerve diseases, stroke and dementia. We investigated the effects of diabetes on apoptosis and mitosis in the hippocampal CA1 region. Rats were given diabetes by injection of streptozotocin (STZ). The mass and blood glucose levels of the rats were measured until day 7 of the experiment. The loss of mass index was approximately 10%, and the diabetogenic index was approximately 330% between nondiabetic and diabetic groups. We investigated caspase-3, caspase-7 and Ki 67 levels immunohistochemically for mitotic activity, the TUNEL method for apoptosis and GFAP for astrocyte cell density in the hippocampal CA1 region. We found that apoptotic cells and the number of astrocytes and mitotic activity in the diabetic group were increased significantly compared to controls. Diabetes stimulates apoptosis and promotes cell proliferation in the hippocampal CA1 region, which may impair its homeostasis and function.