Various infections occur in the acquired immunodeficiency syndrome (AIDS); the liver can become infected by mycobacteria, fungi, and viruses (1, 2). We report a rare case of hepatitis due to a microsporidan protozoa of the genus Encephalitozoon (formerly not identified as a separate genus from Nosema) in a patient with AIDS. Encephalitozoonosis is a chronic, often latent, protozoan infection that occurs in various mammals (3, 4). Until now, microsporida have only been reported to cause myositis (5) and infect enterocytes (6) in patients with AIDS. A 35-year-old homosexual man was well until 4 months before his last hospitalization. He developed