Objective To evaluate factors associated with aortic enlargement in patients with a bicuspid aortic valve (BAV) and the impact of isolated aortic valve replacement (AVR). Design and setting A retrospective analysis of clinical data in a tertiary referral hospital. Patients and main outcome measures We performed a cross-sectional analysis of 595 patients with BAV to assess variables determining maximal ascending aortic dimension. To measure annual dilatation rates, baseline and follow-up echocardiograms were analysed in 70 patients with BAV (BAV-AVR group) and 48 with a tricuspid aortic valve (TVA-AVR group) who underwent isolated AVR, and compared with 65 patients with BAV who did not undergo AVR (BAV-NAVR group). Results Aortic regurgitation (AR) severity was associated with aortic sinus diameter (pConclusions Age-dependent aortic enlargement associated with significant valvular dysfunction and the protective effects of isolated AVR in patients with BAV indicate that valvular dysfunction is a major determinant to the development of aortopathy.