72 T-cell lymphomas were analyzed for the presence of Epstein-Barr virus DNA using Southern or dot blot hybridization. EBV DNA was found in 25 peripheral T-cell lymphomas and in none of 6 T-lymphoblastic tumors. A high prevalence of EBV was detected in AILD type, Lennert's, pleomorphic medium and large cell nodal lymphomas and in upper aerodigestive tract lymphoma biopsies. Clonotypic analysis revealed monoclonal as well as oligoclonal viral populations. The possible influence of EBV in lymphomagenesis, the impact of virus-mediated interactions in the B- and T-cell system and factors involving site of tumor development are discussed.