Etretinate is a synthetic analog of retinoic acid closely related to vitamin A that is used therapeutically in the treatment of severe recalcitrant psoriasis. It is a second-generation orally active retinoid that exerts its effects by binding to specific nuclear receptors and modulating gene expression. Etretinate is available by prescription under the trade names Tegison® and Tigason®, but is gradually being replaced in the armamentarium by its active metabolite, acitretin, another developmental toxicant. In the laboratory, etretinate is a potent developmental toxicant and teratogen in all four animal species tested. In the human, known to the US Food and Drug Administration from 1969 to 1990 were 21 cases of malformations associated with spontaneous abortion in some resulting offspring of women treated with etretinate either during pregnancy or following cessation of treatment with the drug. Etretinate is a large molecule with extended conjugation of double bonds. It is of low polarity and has a low propensity for hydrogen bonding.