In experiments on the bone marrow of mice and a leukocyte culture of human peripheral blood, the cytogenetic activity of cineb, cirame and maneb was revealed. Their embryotoxic effect on rats was shown in comparatively high doses, not toxic for the adult organism. This indicates potential danger of these substances according to both indices. Genetic studies for hygienic purposes must be conducted on biological subjects far removed from man, in particular, on insects. The potential and possible actual genetic danger of pesticides can be assessed on the basis of comparing data from tests on human cells 'in vitro' and on the entire organism of laboratory animals.