Background: Infections caused by Varicella Zoster virus in children with cancer have a high rate of complications and mortality. Aim: To report the outcome of this infection in children with cancer. Patients and methods: Retrospective analysis of medical records of 216 children aged less than 15 years old with the diagnosis of an hematological or solid tumor, admitted to the National Program of Antineoplastic Drugs (PINDA). Results: Eighty seven children had a Varicella Zoster virus infections, 73 (84%) had varicella, 8 (9%) had herpes zoster and 6 (7%) had varicella and herpes zoster. Ninety four percent acquired the infection during antineoplastic treatment and 78% received Acyclovir as antiviral therapy. During a nosocomial outbreak of varicella, three patients with an Acute Lymphoblastic leukemia died in the initial phase of chemotherapy, in spite of an early administration of Acyclovir. No patient with herpes zoster died. Conclusions: The incidence of varicella was higher in children with leukemia or lymphoma than in children with other types of cancer. Virus reactivation was uncommon and had a benign course. Varicella mortality in these children could be favorably modified through an active immunization of immunocompetent children (Rev Méd Chile 2003; 133: 759-64)