The effect of a mixture of scopolamine and hyoscyamine (98:2) on developing chick embryos was investigated. The embryos were exposed at 2 stages of development to various doses of this mixture via yolk sac injection. This resulted in deaths at different stages of prenatal development, as well as various malformations and reduction deformities. These findings suggest that the studied mixture has a teratogenic effect when injected into the yolk sac of developing chick embryos.