The occurrence of Epstein-Barr virus-associated smooth-muscle tumors in immunocompromised patients has been reported, particularly in the pediatric population. In posttransplantation tumors, the tissue of origin has been either donor or recipient. Mixed-genotype sarcomas within the same patient have not yet been reported. We describe the occurrence of multiple leiomyosarcomas of both donor (arising in the lung allograft) and recipient (arising in the host liver) origin in a 15-year-old boy 3 years after heart-lung transplantation. Analysis of premortem lung tumors demonstrated the presence of Epstein-Barr virus DNA. Despite decreasing immunosuppression and commencing acyclovir, the patient died of systemic Pseudomonas infection. Immunohistochemical analysis revealed that both lung and liver tumors were negative for the Epstein-Barr virus receptor (CD21), and suggests that Epstein-Barr virus entry into the cells was not via this receptor but via an alternate mechanism such as cell fusion.