Cultures for free-living amoebae were made from feces of 620 individuals of which 514 were patients from the University Hospital Pedro Ernesto (Rio de Janeiro) and, 106 were children and adults of an orphanage. Positive results were obtained in 70 specimens (11.2%), 55 from the hospital patients and 15 from the orphanage. 60 Acanthamoeba, 6 Vahlkampfia, 5 Hartmannella and, 1 Echinamoeba were isolated. Some individuals were repeatedly positive for Acanthamoeba during the 2 months of observation. Of the isolated Acanthamoeba, 28 were inoculated intranasally. 16 Strains (57.1%) were reisolated from brain and or lungs of the animals. The histopathology revealed an acute inflammatory process with polymorphonuclear neutrophils and amoebae in the brain and lungs of some of the animals. The isolation of pathogenic strains of Acanthamoeba from human feces supports the hypothesis of eventual development, in carriers, of granulomatous amebic meningoencephalitis as an opportunistic endogenous infection.