Phosphodiesterase type-5 (PDE-5) inhibitors are well tolerated and efficacious treatments for male erectile dysfunction that currently rank among the best-selling drugs worldwide. Since their introduction 10 years ago, there have been a number of reports of patients developing, within hours of PDE-5 inhibitor use, permanent visual loss due to nonarteritic anterior ischemic optic neuropathy (NAION), a common optic neuropathy that results from ischemia of the optic nerve head. In some of the cases, visual loss recurred upon rechallenge with the drug. However, as the bulk of the evidence suggesting a relationship between PDE-5 inhibitor use and NAION comes from case reports and small series, it is difficult to ascertain if a cause-effect relationship truly exists. In this paper, following a review of the transient visual side effects of PDE-5 inhibitors and NAION, we discuss the evidence for and against NAION occurring as a complication of PDE-5 inhibitor use.