OBJECTIVE: To investigate dilatory changes of the aorta distal to the root in patients with Marfan's syndrome. METHODS AND RESULTS: Data of 268 patients with Marfan's syndrome who were enrolled in the Euro Heart Survey on adult congenital heart disease were analysed. Data used for this study were baseline characteristics, diameters at four levels of the aorta and events during follow up (dissection, aortic repairs and death). At inclusion, 26 patients had a previous dissection and 53 patients without a previous dissection had undergone elective aortic repair, thus leaving 189 patients without previous dissection or repair. During follow up (median 5.4 years), four patients died. A total of 46 aortic events (dissection or elective surgery) occurred in 45 patients, in the distal aorta in 14 patients (31%). Baseline aortic diameter at the levels distal to the root (arch, descending aorta and abdominal aorta) was greater in patients with than in those without a previous elective aortic root intervention (median 26 mm v 24 mm, p = 0.01; 25 mm v 20 mm, p < 0.01; and 20 mm v 17 mm, p < 0.01, respectively). Multivariate analysis showed that a previous elective aortic intervention was associated with a fourfold increased probability of dilatation of the distal aorta, after adjustment for age and sex (p < 0.01). In patients without a previous intervention, the baseline diameter of the descending aorta was an independent predictor of aortic events (hazard ratio 3.0 per quartile, 95% CI 1.5 to 5.9, p = 0.002). Cause for concern is that complete measurements of the aorta (at least one measurement at each level at baseline or during follow up) were available for only 38% of the patients. CONCLUSIONS: Almost one in every three aortic events occurring during follow up of these patients involved the distal aorta. After elective aortic root replacement, a dilated distal aorta is more common than before. Moreover, an increased diameter of the descending aorta is associated with a higher risk of aortic events in patients without previous dissection or aortic root replacement, independent of the diameter of the aortic root. Careful monitoring of the entire aorta is essential for the optimal management of patients with Marfan's syndrome, especially after elective surgery, but is insufficiently performed in Europe.