Aortic dissection occurs in Turner syndrome with substantially higher frequency in comparison to the general population, and its prevention is one of the main aims of cardiologic follow-up. Findings of cystic medial necrosis in the aortic wall and a high prevalence of aortic dilation suggest that a form of aortopathy exists in Turner syndrome. However, little is known about natural development of aortic dilation prior to dissection. We present a 16-year-old girl with Turner syndrome with a bicuspid aortic valve, aortic stenosis, and dilation of ascending aorta, who underwent annual echocardiographic examinations from early childhood. Significant progressions of proximal aortic dilation occurred twice at the age of 10 and 15 years. Thereafter, another rapid progression was observed during 8 months and within 3 weeks preceding dissection. Acute aortic dissection was diagnosed while the girl was waiting for elective surgery. She was successfully operated. Frequent estimations of aortic diameter in Turner patients with abnormal findings may help to anticipate this life-threatening event. Additionally, we learned that rapid progression of aortic dilation should lead to immediate surgery to prevent more risky urgent intervention following the dissection.