Aortic root dilation (AoD) imparts increased risk of aortic complications such as dissection, rupture, and valvular regurgitation. Multiple etiologies of AoD exist, such as Marfan syndrome, bicuspid aortic valve, Ehler-Danlos syndrome, infections, and idiopathic conditions. Due to the variety of clinical conditions that can result in AoD, and the risks associated with worsening AoD, a thorough understanding of the pathophysiology of AoD, noninvasive imaging modalities, and pharmacologic therapies is critical. This chapter will review the various etiologies of AoD, pathophysiological basis of each disease entity, overview of the diagnosis of AoD, noninvasive imaging modalities employed for detection and surveillance, pharmacological therapies used in the prevention and management, and the factors that guide intervention such as surgical repair.