Idiopathic pulmonary fibrosis (IPF) is a clinical syndrome in which the precipitating factors are unclear. An association between Epstein-Barr Virus (EBV) and IPF had previously been suggested using serology and immunohistochemistry. This study sought confirmation of the presence of EBV DNA in the lung tissue of patients with IPF. Lung tissue obtained surgically from 27 patients with IPF and 28 control subjects was investigated for the presence of EBV by immunohistochemistry and polymerase chain reaction (PCR) analysis. Immunohistochemistry used antibodies specific for EBV lytic cycle antigens (gp340/220 and VCA). Nested PCR analysis used oligonucleotide primers specific for EBV and was sensitive to one copy of EBV DNA. Twelve of the 27 patients with IPF (44%) and three of the 28 control subjects (10%) were EBV positive by immunohistochemistry (p = 0.005). Thirteen of the patients with IPF (48%) and four of the control subjects (14%) were EBV positive by PCR (p = 0.007). Eleven of the patients with IPF (41%) and none of the control subjects were EBV positive by both immunohistochemistry and PCR (p = < 0.001). These data further suggest an association between EBV and IPF. In addition it defines a novel method for detecting EBV in lung tissue. EBV may be involved in the pathogenesis of the disease; however, further studies are required to establish a causal relationship.