A retrospective analysis of early and late outcome for late (>4 weeks) reoperations on the ascending aorta or aortic root. During a 24-year interval, starting in 1974, 834 patients underwent replacement of the ascending aorta (39.2%) or aortic root (60.8%). During the same period, 56 patients with a mean age of 51.1 +/- 14.4 years underwent reoperation after ascending aortic or aortic root replacement. Predominant indications for reoperation were false aneurysm in 25 (44.6%) patients and true aneurysm in 18 (32.1%) patients. Most frequent surgical procedures were redo aortic root replacement in 30 (53.6%) patients and closure of a false aneurysm in 14 (25.0%) patients. Median interval between the operations was 51 months. Eighteen (32.2%) patients underwent concomitant partial or total aortic arch replacement. Hospital mortality was 5.4% (n = 3; 70% CL: 2.4-8.4%). Cause of death was low cardiac output in two patients and rupture of the aorta at the distal suture line in one patient. Univariate analysis identified two or more previous operations (P = 0.038) and the interval between initial operation and reoperation for complication of less than 8 months (P = 0.005) as risk factors for hospital death. Multivariate analysis indicated operation for active endocarditis or vascular graft infection as an independent risk factor for hospital death (P = 0.038, odds 14.6). Follow-up was complete, median 3.1 years. Nine (16.9%; 70% CL: 11.7-22.1%) patients died during that period. Estimated survival at 1, 5 and 10 years was 91.2, 84.0 and 76.4%. One patient underwent another reoperation. Estimated event-free survival at 1, 5 and 10 year is 84.3, 72.2 and 65.6%. False aneurysm formation and progression of aneurysmatic disease are the predominant causes for late reoperations after aortic root or ascending aortic replacement. Reoperations can be performed with low hospital mortality and good late results.