The Herpesviridae family is large and found among all vertebrates. The viruses share a common structure and a common biology consisting of a chronic intermittent infection fluctuating between low-level activity (latency) and high-level replication (reactivation). There are eight known herpesviruses of humans, and these form three subfamilies (the alpha-, beta-, and gamma-herpesviruses) that have laboratory and clinical features in common. These characteristics range from rashes to malignancies. The methods for prevention and treatment of these infections are discussed in this chapter.