This study was performed to evaluate the effects of prenatal development of rats were exposed to Polnoks R and its monomer 2,2,4-trimethyl-1,2-dihydroquinoline (TMDHQ) by gavage every day on days 6-15 of gestation at doses equivalent 6%, 13% and 25% of LD50. Polnoks R and TMDHQ administered per os associated with significant maternal toxicity, embryonal lethality, retarded fetal development and congenital defects. Polnoks R induced skeletal malformations, internal hydrocephalus, and hydronephrosis. 2,2,4-trimethyl-1,2-dihydroquinoline produced internal malformations (exencephale, hydrocephalus, anophthalmia, hydronephrosis and renal hypoplasia) and skeletal malformations of ribs and vertebrae. Polnoks R monomer--2,2,4-trimethyl-1,2-dihydroquinoline is used as an antioxidant in elastomer and rubber productions. Polnoks R and its monomer 2,2,4-trimethyl-1,2-dihydroquinoline are teratogenic to rats and induces CNS, kidneys and skeletal defects.