The cardiovascular teratogenicity and embryotoxicity of ephedrine was studied in chick embryos treated after 2.5-6 days of incubation (Hamburger-Hamilton developmental stages 17-28). The embryos were examined on day 14. Cardiovascular malformations were observed in 29% (29/101) of treated embryos. Complicated anomalies, such as double-outlet right ventricle (DORV), truncus arteriosus communis (TAC) or overriding aorta with ventricular septal defect (VSD) were seen frequently in embryos exposed to the agent on day 3 of incubation. Malformations were induced by ephedrine at a dose as low as 1 mumol/egg.