The herpes virus family consists of five viruses: varicella zoster, hominis or simplex, Epstein-Barr, cytomegalovirus, and simiae (a monkey virus that occasionally infects human beings). These DNA viruses are similar in structure and appearance and have a world-wide distribution. This chapter deals exclusively with varicella-zoster virus (VZV) pneumonitis — its pathogenesis, clinical manifestations, diagnosis, management, and prognosis.