Thoracic aortic dissection (TAD) is a catastrophic cardiovascular disease and is thought to have a genetic basis. Various studies have indicated that renin-angiotensin system plays an important role in the pathogenesis of aortic disease. To determine the association of the I/D polymorphism of ACE gene with the risk of TAD in a Chinese Han population, a hospital-based case-control study was designed consisting of 161 subjects with TAD and 256 control subjects. The genotype frequency of the ACE I/D polymorphism was determined by using a polymerase chain reaction assay. The overall distribution of ACE I/D genotypes was significantly different between the two groups. Compared with the controls, the frequency of DD genotypes and the D allele of ACE gene were significantly increased in TAD patients. Multivariate logistic regression adjusting for conventional vascular risk factors confirmed the association between the ACE I/D polymorphism and the susceptibility to TAD (OR 2.14, 95 % CI 1.38-3.32, P = 0.001). Our data demonstrated that the ACE I/D polymorphism appeared to be an important risk factor in the development of TAD. However, further validation in large population-based studies is needed to confirm the finding.