Three cases of intestinal microsporidiosis are reported, in acquired immunodeficiency syndrome patients, with a chronic diarrhea. The first case is associated with an intestinal cryptococcosis and with a cytomegalovirus infection and the second case was diagnosed on ileal biopsy specimen. Since the first description of Enterocytozoon bieneusi in 1985. 49 cases of intestinal microsporidiosis are reported in the literature, all in AIDS patients and the frequency of this infection is probably underrated. Prospective studies find it in 6 to 30% of cases. This parasite must be suspected in HIV seropositive patients with clinically chronic unexplained diarrhea or with intestinal atrophy.