We report herein a case with acute hepatitis due to hepatitis B virus genotype Ae, concurrent with amebic colitis. A 39-year-old homosexual Japanese man was admitted to our hospital with jaundice. Laboratory tests showed an elevation of transaminase and positivity for hepatitis B surface antigen and IgM-type antibody to hepatitis B core antigen. The hepatitis B virus genotype was determined to be Ae. Furthermore, a mud-like stool with blood and mucous had sometimes been noted during the past 3 years, and amebic colitis was shown by colonofiberscopy during hospitalization. The patient was diagnosed with acute hepatitis B, concurrent with amebic colitis, and was successfully treated with lamivudine and metronidazole. In Japanese patients with acute hepatitis B virus genotype A infection, homosexual activity tends to be high. Furthermore, in Japanese homosexual men, amebiasis has been increasing. Thus, in Japanese patients with acute hepatitis B, a determination of genotype should be performed in order to investigate the route of transmission of hepatitis B virus, and a search for amebiasis should be performed in patients with acute hepatitis due to hepatitis B virus genotype A. Furthermore, education of homosexual men regarding hepatitis B virus, hepatitis B virus vaccination, and amebiasis is urgently required.