Backgrounds: Some aortic aneurysm (AA) or aortic dissection (AD) patients can be observed to detect disease progression if optimal blood pressure (BP) is achieved. However, in another group of patients, disease progression occurs despite well-controlled BP. There is no clear data to explain the difference in clinical outcomes in these patients. The aim of this study is to determine if central aortic pressure (CAP) can be a prognostic marker in AA and AD. Methods and Results: Fifty-six newly diagnosed AA or AD patients who did not have an urgent need to undergo surgery or interventional treatment were enrolled. All patients achieved brachial systolic blood pressure (SBP) ���120 mm Hg with beta-blocker based treatment within 1 month. Then, CAP parameters were noninvasively checked with radial tonometry (SphygmoCor짰 Px Pulse Wave Analysis System, AtCor Medical, Sydney, Australia). All patients were monitored for at least 6 months and for as long as 5 years. Thirty-three patients did well without disease progression. However, disease progression was noted despite well-controlled brachial BP in 23 patients. In intergroup comparisons, central aortic systolic pressure (CASP; 112.7짹3.5 mm Hg vs. 104.3짹7.5 mm Hg) and aortic augmentation index (AI: 33.4짹13.5% vs. 23.4짹8.7%) were significantly high in the disease progression group (p<0.05). Conclusion: In some AA or AD patients, CASP and AI can be considered as surrogate prognostic markers. CAP monitoring can be superior to conventional brachial BP monitoring in AA and AD.