A possible role for hepatitis C virus (HCV) infection in the pathogenesis of idiopathic pulmonary fibrosis (IPF) has recently been suggested on the basis of an unusually high seroprevalence rate of anti-HCV in such patients from Japan. In an attempt to confirm these findings, we tested sera from 62 patients with IPF by two second-generation anti-HCV ELISAs. Only one serum was reactive. Serum from this patient gave an indeterminate result when tested by four-antigen RIBA (c22 band only), and it was negative for the presence of HCV RNA when tested by the reverse transcriptase polymerase chain reaction assay. HCV infection is thus no more prevalent in patients with IPF from the UK than in the general population.