Sequences which encode Epstein-Barr virus (EBV) RNA in nasopharyngeal carcinoma (NPC) tissue have been identified. We utilized human biopsy material directly as well as NPC grown in nude mice. Total RNA was extracted from the tumor material and separated into polyadenylated and nonpolyadenylated fractions by oligodeoxythymidylate-cellulose chromatography. This material was used as template to construct 32P-labeled cDNA. The labeled cDNAs were hybridized to Southern blots of recombinant EBV DNA fragments. Three of the biopsies, F, 49, and 55, contained polyadenylated RNA homologous to the EBV BamHI fragments V and K, and EcoRI-DIJhet. These same fragments encode the most abundant polyribosomal RNAs in latently infected lymphoblastoid cell lines. The sequences which encoded nonpolyadenylated RNA in NPC tumor 49 were more extensive and included BamHI fragments C, V, B, E, and K, and EcoRI fragments DIJhet, E, F, and G1, a result that indicates selective polyadenylation in EBV RNA processing. A fourth biopsy, NPC tumor 18, contained polyadenylated RNA homologous to the BamHI fragments H, B, K, Y, B1, I1, and A and EcoRI fragments F and G2. A similar pattern of transcription was identified in three tumor specimens from nude mice, 4, 5, and 8. Transformation of lymphocytes did not occur after cocultivation in vitro with explants from these nude mice tumors. This transcriptional pattern may represent an activated state of the EBV genome, formerly not detected in tumor tissue, which is analogous to the state of abortive infection identified in induced in vitro cell systems.