An unidentified organism was found in the stools of 55 immunocompetent patients who presented to the CIWEC Clinic in Kathmandu, Nepal between June and November 1989. The microscopic features of the organism share characteristics of both coccidia and cyanobacteria species. From June 26, 1989 to November 17, 1989, 55 persons were identified as having the organism in at least one stool sample. The illness was characterized by prolonged watery diarrhea, anorexia, fatigue, and weight loss. The mean ± SD duration of illness was 43 ± 24 days (range 4–107). Thirty-four patients received a total of 78 courses of antimicrobial treatment (2.3 courses/patient). The mean ± SD duration of illness in 34 treated patients was 46 ± 24 days. In 14 untreated patients, the mean ± SD duration of illness was 35 ± 23 days. The organism is 8.0–9.0 µm in diameter, floats in Sheather's solution, and stains red with the modified acid-fast stain. Since the agent was closely associated with a prolonged, self-limited diarrheal illness, it could easily have been misdiagnosed as Cryptosporidium. The organism should be looked for in the stools of patients with persistent diarrhea and a history of foreign travel.