ABSTRACT. Objective. Varicella-zoster virus has been reported to produce serious, often life-threatening, disease in immunosuppressed patients with a variety of diagnoses. The impact of this virus on the young child after heart transplantation has not been reported.Methods. We reviewed the charts of 28 children who were <10 years of age at heart transplantation and had at least 1 year of follow-up. The median follow-up period was 7 years (1.4 -13.0 years). All were seronegative for varicella-zoster virus before transplantation. Fourteen (50%) developed varicella at a median time posttransplantation of 3.3 years. The first 7 were admitted for intravenous acyclovir for 3 days followed by oral acyclovir for 7 days. The last 7 were treated as outpatients with oral valacyclovir for 7 days (n ‫؍‬ 6) or with oral acyclovir for 10 days (n ‫؍‬ 1).Results. Intravenous and oral regimens both were well tolerated and were without complications. No patient was receiving steroids at the time that they developed their initial episode of varicella. One patient was receiving steroids for therapy of posttransplantation lymphoproliferative disease when she developed recurrent varicella or generalized zoster. No episodes of rejection were attributed to the varicella-zoster virus infection. There were no episodes of localized zoster. All patients experienced seroconversion from undetectable to detectable antibody titers early after varicella, and 12 of the 14 patients continued to have persistent detectable titers in late follow-up. Two of the 14 who received chemotherapy or enhanced immunosuppression after retransplantation transiently lost detectable varicella-zoster virus antibodies but currently have detectable titers.Conclusions. Primary varicella-zoster infection was well tolerated in our young pediatric heart transplant recipients, with no serious complications. We now reserve inpatient/intravenous therapy for those who are unable to tolerate oral medications or those who are receiving enhanced immunosuppression. Pediatrics 2001; 108(5). URL: http://www.pediatrics.org/cgi/content/full/ 108/5/e80; heart transplantation, varicella, pediatric.ABBREVIATIONS. VZIG, varicella-zoster immune globulin.