We report a case of a male 49 years old, without clinical history, excepting rape in 1996, that was admitted to the Emergency Room of HGUGM because of diarrhea 6 months duration, plus fever (39 degrees C) in the last 2 months. He was diagnosed of infection by the Human Immunodeficiency Virus (HIV), with serum antigenemia (70 cells), and colonic biopsy positives for Cytomegalovirus, and a normal colonoscopy. Cytomegalovirus colitis is the major etiologic infectious agent in patients with AIDS-associated diarrhea, although it can be the diagnostic index for AIDS in a few cases.