Four indoor swimming pools in recreation centres in the city of Belgrade were tested to the presence of free living amoebae (swimming pool water, step smears, smears under the showers). As the consequences of people's infections caused by these amoebae are now well know, the goal of our investigation was to prove their possible presence, and to establish pathogenic potential of the isolated species. Only one of the isolated strains of the Acanthamoeba genus was cytopathogenic to the Vero cell culture, and it caused microfocal pneumonitis in laboratory animals. The results published in this work point out to the needs for introduction of regular parasitological control of the swimming pools in order to decrease the risk of infection and to avoid infections in people by pathogenic free living amoebae.