The pathophysiological mechanisms of diabetic impotence remain obscure. We have presented an analysis of sexual function in a diabetic rat (BB/WOR) model characterized by diffuse neuropathic changes without a confounding vasculopathy that allows us to define the neural components of erectile failure. Copulatory behavioral testing demonstrated that diabetic males were severely impaired: the controls mounted three times more than the diabetics and had about one-half the latency to first mount. The diabetics had about one-fourth the number of intromissions and took nearly twice as long to achieve first ejaculation. The number of ejaculations was drastically reduced as well. We examined sexual reflexes in the anesthetized acutely spinalized rat. These experiments tested the integrity of spinal circuits controlling sexual function. Reflex testing demonstrated that spinal sexual reflexes were also severely impaired: the onset latency of reflexes was more than doubled, and the duration of reflexes was less than one-half. More than one-half of the diabetic rats showed no penile erections. Neural studies showed even more derangement in reflex measures in rats, without erection. Nerve conduction velocity experiments suggested a peripheral neuropathic change in hypogastric nerve and motor pudendal nerve fibers. These dysfunctional findings were seen without any androgen deficiency. These results indicate that diabetic impotence in this model reflects central and peripheral neuropathic disease processes.