SummaryA case of thallotoxicosis during the first trimester of pregnancy is presented.Thallium intoxication during pregnancy or during embryogenesis can cause abnormalities, especially skeletal, in laboratory animals.Up to now six cases of human thallium intoxication during the first trimester of pregnancy have been reported. No congenital abnormalities were mentioned but on these data no definitive conclusion can be drawn. When intoxication occurs after the first trimester, only some of the newborns have symptoms compatible with thallo-toxicosis.Among these symptoms are mentioned alopecia, rash, low birth weight and premature birth. Serious intoxication of the mother at the end of pregnancy can cause the death of the newborn.Abortion never occurred when thallium was taken for this purpose.