RESUMEN
Blastocystis hominis is a polymorphic protozoan of discussed taxonomic position, which is currently associated with human intestinal disease. In order to determine the prevalence of the microorganism in a sample of hospitalized patients, a study was carried out from november 1996 to april 1997 on 100 adult patients of both sexes aged 20 to 79 years at the Ruíz y Páez University Hospital of Bolivar city, Venezuela. A coproparasitological study was carried out using direct examination and Faust method. Infection by parasites and/or commensals was demostrated in 48 patients. The most frequent agent was B. hominis with a prevalence of 42,0 percent. We did not find a statistically association between sex (p > 0,05) or age (X²=3.52: d.f; =3) and B. hominis infection. B. hominis was most frequently identified as the single parasite (88,1 percent), and with a number of less than 5 cells per 400X microscopic field (73,8 percent). The infection was more common in patients with base chronic-immunosuppressive diseases, the major one being cancer. Diarrhea was observed in 27,0 percent of cases. Due to its high prevalence, especially as a single agent, together with the particular immunological characteristics of the patients studied, a potential pathogenic role of the opportunistic type is suggested for B. hominis