Broad-Breasted White turkeys were randomized into four treatment groups at 4 weeks of age in each of three trials. Group 1, males, and Group 2, females, were fed an unsupplemented (control) diet from 4 to 10 weeks of age. Group 3, males, and Group 4, females, were fed the control diet supplemented with 0.07% beta-aminopropionitrile (BAPN). The experiments were terminated at 10 weeks of age. There was no mortality among male and female turkeys fed the control diet or significant differences in blood pressure, heart rate, aortic tensile strength, or aortic hydroxyproline between these males and females. Sixty-five percent of the males and 21% of the females fed BAPN died of dissecting aneurysms; blood pressure, heart rate, and dp/dt max were not altered as a result of feeding BAPN. Aortic tensile strength was higher in control turkeys than those fed BAPN, but males fed BAPN had the lowest value. Males fed BAPN also had the lowest aortic hydroxyproline content. Ultrastructural alterations of aortic elastic and collagen fibers were more severe in males than females fed BAPN. Aortic changes did not occur in control turkeys.