During 35 years from 1971 to 2005, 153 patients with acute and 4,277 with chronic HBV infection visited the Toranomon Hospital in Tokyo, Japan. They were grouped into seven 5-year periods, and HBV genotypes/subgenotypes were determined. Patients with acute HBV infection were younger (P = 0.046), predominantly male (P = 0.004), possessed higher alanine aminotransferase levels (P < 0.001), positive more frequently for HBeAg (P < 0.001), and had lower HBV DNA loads (P = 0.014) than those with chronic infection. Sexual transmission was more frequent in patients with acute than chronic HBV infection (67% vs. 3%, P < 0.001). The number of patients with acute infection increased throughout 1971–2005. Patients with chronic infection increased since 1971, peaked in 1986–1990 and then decreased. The number of patients increased since 1990–2000 again, however, reflecting recent boost of acute HBV infection. The distribution of HBV genotypes was considerably different between patients with acute and chronic infections (A, B, and C: 28.6%, 10.3%, and 59.5% vs. 3.0%, 12.3%, and 84.5%, respectively, P < 0.001). Since 1991, genotype A foreign to Japan started to increase sharply in patients with acute infection, and gradually in those with chronic infection. There was a trend for the foreign subgenotype B2/Ba to increase recently (P < 0.05). Despite immunoprophylaxis of high-risk babies born to carrier mothers with hepatitis B e antigen, implemented nationally since 1986, acute and chronic infections with HBV have been increasing in Japan. Based on genotypes/subgenotypes changing with time, the resurgence of hepatitis B could be attributed to infections, with foreign HBV genotypes/subgenotypes, spreading swiftly by sexual contact. J. Med. Virol. 80:1880–1884, 2008. © 2008 Wiley-Liss, Inc.