Erectile dysfunction affects 50 percent of men ages 40-70 in the United States and is considered an important public health problem by the National Institutes of Health. Consumers are exposed to a plethora of natural products claiming to restore erection and sexual vitality. A review of the available empirical evidence reveals most naturally occurring compounds lack adequate clinical trials to support efficacy. However, arginine, yohimbine, Panax ginseng, Maca, and Ginkgo biloba all have some degree of evidence they may be helpful for erectile dysfunction. Improvements in penile endothelial L-arginine-nitric oxide activity appear to be a unifying explanation for the actions of these naturally occurring agents.