The development of infection remains a significant source of morbidity and mortality in the oncology patient. This patient population is at increased risk for infection because of alterations in cell-mediated immunity generated by the underlying neoplastic process and/or immunosuppressive therapy. Viral infection, particularly that attributable to herpes simplex virus (HSV), is being seen with increased frequency in the oncology patient. Because effective therapy is available with the early use of antiviral agents, it is important to be aware of the potential for viral infection and to recognize the signs and symptoms that are evident early in its course. An overview of HSV infection is provided here, including discussion of the virus itself, its pathogenesis, its clinical spectrum, and current prophylactic and therapeutic approaches.