INTRODUCTIONONE supposition is that aortic rupture results from a combination of high blood pressure and a weakened aorta. The arterial blood pressure of the turkey is highest of any vertebrate and has a characteristic increase during the growing period (6 to 20 weeks of age) (Ringer, 1959; Krista et al., 1965). The presence of atheromatous plaques is a common occurrence in the posterior aorta of the turkey and may provide a weakening effect. Carnaghan (1955) and Gibson and de Gruchy (1955) have observed plaques at the site of rupture and Ball (1964) has reported observing elastic tissue obliteration and fibrosis in the turkey aorta as early as three weeks of age.Diethystilbestrol increased the incidence of aortic rupture and concomitantly reduced blood pressure (Krista et al., 1965; and Simpson et al., 1964). The administration of testosterone reduced the incidence of aortic rupture with no apparent effect on blood pressure (Krista.