The embryotropic effect of the new Bulgarian simtriazine herbicide polyzin 50 was studied in an experiment upon 90 pregnant albino rats - Wistar, via inhalation effect in concentrations 2 mg/m3 and 0.2 mg/m3, daily during the whole pregnancy and at a level of 2 mg/m3 during the first trimester of gestation. With both regimes, the preparation has a teratogenic and a more lightly manifested embryotoxic activity. In the absence of general toxic effect upon the pregnant organism, polyzin induces external malformations (hypognathus, oedema), anomalies in the development of the internal organs (hydrocephalus, intracerebral hematoma, hemorrhages in the abdominal cavity, infarctus-like foci in liver) and defects in the ossification of the cranial bones of fetus. The preparation has an embryotoxic activity (increased incidence of subcutaneous hematomas of the fetus), only with the daily penetration in organism of the pregnant animals in a concentration of 2 mg/m3. With both concentrations of antenatal effect of polyzin studied, a functional insufficiency of the liver of the progeny develops during the postnatal development period. On the grounds of the data obtained about the embryotoxic and teratogenic effect of polyzin with its inhalation effect in low concentrations - 2 mg/m3 and 0.2 mg/m3, a recommendation is proposed-prohibition of women's participation in its production at a fertile age.