This structure-activity model of teratogenicity was developed to provide the ability to rank untested compounds by their probability of teratogenicity. The model is based on 430 compounds collected from various sources in the literature and scored from zero to one as to evidence of teratogenicity. A discriminant equation then separates those compounds in the extremes of this distribution. The false positive classification rate based on the compounds in the equation is approximately 8% and the false negative rate approximately 10%. Approximately 22% of the compounds are not classifiable as either teratogens or nonteratogens with this equation.