Elevated level of homocysteine in blood serum of pregnant women is the risk factor for placental malfunction and fetal abnormalities. Our study has shown the activation of apoptosis, inhibition of proliferation, destruction of placental trophoblast and activation of the transsulfuration pathway under elevated homocysteine level in the incubation medium in the range of 20-80 microM. The activation of the transsulfuration pathway indicates that placenta may to some extent withstand elevated homocysteine level.