Varicella-zoster virus (VZV) causes significant morbidity and even mortality in immunocompromised patients. Varicella has more serious consequences than herpes zoster, although zoster is more common. This paper reviews the natural history of varicella-zoster infections, as well as strategies for prevention and treatment. Although initial studies supported the use of either vidarabine or acyclovir for treatment of varicella in immunocompromised children, subsequent data have shown acyclovir to be superior for this purpose. Recent data in bone marrow transplant patients indicated that acyclovir was also more effective in preventing progression of herpes zoster in the immunocompromised host. The question of using steroids to prevent postherpetic neuralgia remains controversial. With the advent of effective antiviral chemotherapy, treatment of VZV infections in the immunocompromised host has become a reality. The potential problem of acyclovir-resistant VZV strains justifies continued development of other anti-VZV agents. Several new compounds are presently in or slated for clinical trials.