RESUMEN
Large-scale surveys of representative population groups (n = 2243) in 7 cities and 3 provinces of the central, Povolzh'e, and northwestern regions of the Russian Federation provided the basic epidemiological features of cryptosporidiosis in the European part of the country. Its mean incidence of the population was 3.34%, much higher in children (3.69%) than in adults (0.41%). The boys were more frequently afflicted than the girls (4.69% versus 1.92%). There were no differences in the infection rates between rural and urban children. Young children (aged 1-3 years) with diarrhea and children in closed collective bodies are infection risk groups. The detection rate of persons infected with Cryptosporidium was much greater by the formalin-ether precipitation technique than that by the routine smear test. The correlation coefficient as to the infection rates detected by the routine smear tests was 1.75.