Hypertensive and hypotensive lines of turkeys were treated with diethylstilbestrol (DES) alone, or with DES and propranolol (PROP). Untreated turkeys of each blood pressure line served as controls. Mortality rate from aortic ruptures was highest (43.7%) in the hypertensive line treated with DES, but mortality was reduced to 7.7% when this line of turkey was treated with both DES and PROP. Among the hypotensive line of turkeys treated with DES, 26.7% died of aortic ruptures, but none died when these turkeys were treated with DES and PROP. Propranolol did not influence serum cholesterol levels, and all DES or DES and PROP treated birds had greatly elevated values, as contrasted to untreated turkeys. Aortic lipid values were highest in the hypotensive line of turkeys treated with DES, but, by histologic evaluation, aortic atherosclerosis was equally severe in all DES-treated turkeys. Blood pressure and aortic dp/dt max were higher in the hypertensive line treated with DES than in the similarly treated hypotensive line. This probably accounted for the higher mortality in the former group. Absence of significant mortality in either line of turkey following treatment with both DES and PROP apparently resulted from the decreased stress on the aorta caused by lowering of blood pressure and aortic dp/dt max by PROP.