BACKGROUND The natural history of the residual aorta after repair of acute type A aortic dissection is incompletely understood. METHODS During a 22-year period, 201 patients underwent repair of acute type A dissection by 25 surgeons. For 168 operative survivors, mean late follow-up for reoperation or death was 6.5 +/- 5.5 years and was 100% complete. Late blood pressure and medication history were available for 136 patients. Overall, 412 computed tomography scans were analyzed for segmental diameter and false lumen patency from 69 patients who underwent multiple follow-up imaging studies at our institution. RESULTS Freedom from reoperation at 10 years (range, 1 to 170 months) was 74% +/- 5% (28 reoperations in 26 patients). A nonresected primary tear (p = 0.05), Marfan syndrome (p < 0. 001), elevated systolic blood pressure at follow-up (p = 0.008), and absence of beta-blocker therapy (p = 0.02) were independent predictors of late reoperation. Aortic growth between consecutive imaging studies was detected in 18% of intervals (62/343) affecting 49% patients (34/69), with mean yearly growth rate of 5.3 +/- 4.5 mm. Onset of enlargement was unpredictable and occurred 59 +/- 45 months postoperatively (range, 1 to 167 months). Risk factors for growth included aortic diameter (p < 0. 001), elevated systolic blood pressure (p = 0.04), and presence of a patent false lumen (p = 0.05). Maximum aortic diameter of less than 35 mm predicted growth in 11% of intervals, 35 to 49 mm in 22%, and more than 49 mm in 37% (p < 0.001). Different proximal or distal surgical strategies did not affect aortic growth or need for reoperation (p > 0.17). CONCLUSIONS Optimal long-term outcome of patients with acute type A dissection demands rigorous antihypertensive therapy and lifelong radiographic follow-up because aortic enlargement can begin more than a decade postoperatively.