Erectile dysfunction (ED) is an increasingly common problem in the aging population and has been associated with chronic heart failure (HF), either as an epiphenomenon or even as an early marker for underlying cardiovascular disease. ED has a significant effect on patients' quality of life. This chapter reviews ED in patients with HF and prevention and treatment based on current data from the literature. Causes include physiologic changes resulting in decreased cardiac function and exercise capacity, intrinsic vascular and neurohormonal abnormalities, and extrinsic factors such as medication side effects and psychological issues. Physicians should address these issues with patients and begin treatment by optimizing HF management and minimizing medications with ED side effects. Use of phosphodiesterase-5 inhibitors provides significant improvement of ED and quality of life. Further research still is needed regarding long-term effects of ED treatment, investigation of newer medications, and preventive measures in this patient population.