Four nasopharyngeal carcinomas (NPC) with positive Epstein-Barr virus serology were successfully grafted into athymic mice. Tumor growth could be maintained up to the 22nd passage. Strong similarity between original NPC biopsies and xenografts is demonstrated in terms of light microscopy and immunohistochemistry. Growth kinetics show an increase of tumor volume doubling time and a decrease of the labeling index after several passages. Xenografting of NPC into nude mice is evaluated as a useful in vivo tumor model for experimental NPC investigation.