Enterocytozoon bieneusi, a microsporidian parasite, has been recognized since 1985 as an agent of intestinal microsporidiosis leading to malabsorption syndrome, diarrhea, and weight loss in AIDS patients. Recently, however, we have identified E. bieneusi spores in the sputum, bronchoalveolar lavage, and stool samples of an AIDS patient with a 2-year history of intestinal microsporidiosis. The s...