Background: Previously published studies of microsporidial infections have primarily focused on immunodeficient or immunocompromised patients. Data regarding infections caused by this microorganism in immunocompetent subjects are lacking. In the present study, we investigated the prevalence of microsporidia in healthy individuals and immunocompetent patients with acute and chronic diarrhea. Methods: The study included stool samples from 74 patients with acute diarrhea, 41 patients with chronic diarrhea, and 88 healthy volunteers. Slides were prepared after concentration with a formalin-ethyl acetate technique and were stained with modified trichrome, calcofluor white, and Uvitex 2B stains. The number of spores observed in each magnification field (x1000) was scored as follows: 1+, 1-10; 2+, 11-20; 3+,>20. Results: The prevalence of microsporidia was 27.0% in patients with acute diarrhea, 34.1% in patients with chronic diarrhea, and 45.5% in healthy volunteers. The parasite score was 1+in all positive samples. The rate of microsporidia positivity was higher in solid stools (51.4%), and the rate of positivity increased with advancing age. Conclusion: Unexpectedly, a high prevalence of microsporidia was found in immunocompetent individuals in our region. There was no relationship between positivity for microsporidia and the presence of symptoms, due to higher rates both in solid stools and in healthy subjects. The parasite score was the same in all groups. Our results indicate that there is high exposure to microsporidia in immunocompetent subjects in our region. Natural reservoirs and environmental sources of microsporidia should be determined to design strategies for effective prevention of transmission.