Seven cases of primary lung lymphoma were analyzed for the presence of Epstein-Barr virus DNA sequences by the polymerase chain reaction. The series included: four cases of diffuse, small lymphocytic lymphoma; one case of diffuse, intermediate lymphocytic lymphoma; one case of diffuse, small cleaved cell lymphoma; and one case of large cell, immunoblastic lymphoma. The latter occurred in a patient with acquired immunodeficiency syndrome. A 200-bp sequence of the Epstein-Barr nuclear antigen 1 gene was used as a template for PCR amplification. The only tumor that contained Epstein-Barr virus sequences was the immunoblastic lymphoma. These findings support previous observations that small lymphocytic lymphomas of the lung are not related to Epstein-Barr virus infection. In contrast, some large cell lymphomas may represent Epstein-Barr-virus--associated lymphoproliferative disorders.