Herpes virus (cytometalovirus [CMV], herpes simplex virus, varicella zoster virus) and invasive fungal infections continue to cause significant morbidity and mortality in allogeneic hematopoietic cell transplant (HCT) recipients despite the availability of effective therapies. In this study, we developed an Internet-based survey, which was distributed to all hematopoietic cell transplant centers participating in the Center for International Blood and Marrow Transplant Research (CIBMTR) program, to gather information on strategies utilized for the prevention of disease caused by herpes viruses and fungal infections between 1999 and 2003. The survey response rate was 72%, representing 175 programs from 32 countries. Generally, reported center strategies were in accord with the Center for Disease Control and Prevention guidelines published in 2000, with 81% of programs using low-dose acyclovir prophylaxis for herpes simplex virus seropositive patients, 99% of programs reporting use of a CMV prevention strategy during the first 100 days posttransplant for all patients at risk of CMV disease, and 90% of programs using antifungal prophylaxis. Seventy percent of programs reported routine use of a CMV prevention strategy in high-risk patients after day 100. The greatest departure from published guidelines was the use of acyclovir prophylaxis for varicella zoster virus seropositive recipients in 75% of programs. There were very few reported changes within centers in practices over the study time period. Significant regional variations were found with regard to surveillance procedures and treatment durations. There were no significant differences in treatment practices by center size and very few differences found between those centers that reported treating primarily pediatric patients versus primarily adult patients. In summary, our survey demonstrates overall agreement with published guidelines for the prevention of disease because of herpesviruses and fungal infections with significant regional differences found in duration of antiviral prophylaxis, duration of preemptive therapy, and duration and dosing of antifungal prophylaxis. Center size and age of primary patient population were not associated with many reported differences in strategies.