Reye's syndrome is an acute hepatopathy and encephalopathy affecting children during the convalescent period of a viral infection, frequently influenza B. The role of influenza B in the pathogenesis of Reye's syndrome is unknown. To investigate this relationship, an in vitro system was designed to examine the interaction of influenza B virus with a cell line of human hepatocytes (HepG2) which retains many specific hepatic synthetic characteristics. HepG2 was capable of supporting a productive infection by influenza B, although greater virus inputs were required than in fully permissive Madin-Darby canine kidney cells. Because of the recent association of Reye's syndrome with aspirin use, the kinetics of influenza B growth were studied in the presence of acetylsalicylic acid (25 and 100 μg/ml) and were not found to be altered. Protein synthesis by HepG2 cells was decreased by 80% in influenza B-infected cells when compared to uninfected controls. Acetylsalicyclic acid, 100 μg/ml, did not affect the rate of 35S-methionine incorporation by infected or uninfected HepG2 cells. The rates of synthesis of specific proteins (albumin, transferrin, and apoprotein B) by HepG2 cells were determined by immunoprecipitation of 35S-methionine labeled cell lysates. After 12 h of infection, synthesis of all three plasma proteins was decreased by 40–60%. These studies describe a useful system for delineation of mechanisms by which influenza B virus interacts with host hepatocytes and the host-cell protein synthetic machinery. The studies could be pertinent to the pathogenesis of Reye's syndrome.