Objective: To investigate the therapeutic effects of insulin on erectile dysfunction (ED) in a rat model with streptozotocin-induced diabetes.Materials and methods: The diabetic erectile dysfunction (DMED) rat model was made by injecting the male 8-weekold Sprague-Dawley rats intraperitoneally with vehicle or freshly prepared 60 mg/kg streptozocin, and blood glucose level was measured in the later experiments.Then the rats were divided into three groups: the normal control group (N), the diabetes group (DM) and the diabetes plus insulin therapy group (DM + insulin).Eight weeks after STZ injection, the DM + insulin group were treated with 2-6 units of neutral protamine Hagedorn twice a day for 4 weeks through subcutaneous injection.After the final treatment,all rats were tested for erectile function by measuring the intracavernous pressure and mean arterial pressure (ICP/MAP), and the penile was harvested for histology study.