Twenty-nine cases of lymphomatoid granulomatosis (LYG) were examined for Epstein-Barr virus (EBV) genomes by means of the polymerase chain reaction (PCR) technique on paraffin-embedded formalin-fixed tissue. EBV DNA sequences were identified in 21 cases (72.4%), while five examples of primary well differentiated lymphocytic lymphoma (WDLL) of lung and one metastatic large cell lymphoma to lung (lymph node origin) were negative. These findings support the hypothesis that LYG represents a unique form of lymphoma, and they suggest that its pathogenesis may be related to EBV infection.