Zoonosis has been suggested for hepatitis E virus (HEV) infection, but so far is based only on indirect evidence. We experienced a series of cases of HEV infection among people who had eaten uncooked deer meat 6-7 weeks before. On testing, a left over portion of the deer meat, kept frozen to eat in the future, was positive for HEV RNA, whose nucleotide sequence was identical to those from the patients. Patients' family members who ate none or very little of the deer meat remained uninfected. These findings provide direct evidence for HEV infection to be a zoonosis.