Varicella is predominantly a disease of children, in whom it typically has a benign course and outcome. However, when the disease affects adults, the complications can be life-threatening. Varicella pneumonia, secondary bacterial infection, and opportunistic infection in the immunocompromised host are the most common complications in the adult. Surveillance for these complications is mandatory because appropriate therapy may be life-saving. The introduction of specific antiviral agents may be useful in certain clinical circumstances. The authors describe two representative patients and discuss the diagnosis and treatment. They also discuss this infection in adulthood in general.