The association of a bicuspid aortic valve (BAV) with abnormalities of the proximal thoracic aorta, including dilatation, aneurysm and dissection, has been previously described, leading to the hypothesis of a common underlying developmental defect involving the aortic valve and the aortic wall. Consequently, any patient with BAV should receive a careful assessment not only of the valve function, but also of the aortic root and the ascending aorta. Dilatation of the proximal thoracic aorta is a common finding in patients with BAV and is believed to be related to aortic rupture and dissection. Because progressive dilatation can occur, careful long-term surveillance of the aortic dimensions is required. Prophylactic surgical repair of the dilated aorta should be recommended more aggressively for patients with BAV than for those with a tricuspid aortic valve. However, the optimal timing of aortic surgery in BAV patients remains uncertain because of the limited data available on the natural history of asymptomatic aortic dilatation.