In summary, there are several major findings in the present study including AT1b receptors contributing to AngII-induced aortic contraction that parallels with the mRNA abundance of AT1b receptors in this region, and AT1b receptors not contributing to AngII-induced atherosclerosis and aortic aneurysms in either the ascending or abdominal aortic region. This evidence concerns the gene AGT and aortic aneurysm.