Background : Physical and mental activities can be trigger factors for AD(aortic dissection). Several studies showed that trigger factors were closely related to circadian variation of the onset of AD. The aim of this study is that we investigate the relationship between trigger factors and circadian variation of AD. Methods : 76 consecutive patients excluding 47 patients with intramural hematoma among 123 patients visited Kyungpook National University Hospital between June 2005 and May 2007 were included in the study group. Data were retrospectively collected from the hospital medical records. We divided the patients into two groups : younger(���60 years old) and older(>60 years old) group, female and male, and Stanford type A and B, to assess the influence of age, sex, and anatomical location, respectively. The day was divided into twelve 2-hour and four 6-hour periods to evaluate circadian variation of AD. Results : There were 50 younger group, 47 male group, and 48 Stanford type A group(63.2%). 57 patients(75.0%) including 42(55.3%) physical and 15(19.7%) mental activities had activities as trigger factors of AD. 19 patients(25.0%) had no activities as trigger factors of AD. There showed chronobiologic variation in AD. Triggering activities did not differ between male and female(p=ns). However, older group and Stanford type B were related with no activity than younger(p=0.049) and type A(p=0.024), respectively. In circadian variation presented as four 6-hour periods, Stanford type B was more developed at evening time than type A(p=0.038). However, there was no significant correlation between triggering activities and circadian variation of AD. There was no significant correlation between triggering activities and circadian variation in AD classified as younger and older group, female and male, and Stanford type A and B. Conclusion : There were significant differences of triggering activities and circadian variation between Stanford type A and B of AD. There was no significant correlation between triggering activities and circadian variation in AD. There were also no significant age, gender, and Stanford type-related differences in triggering activities and circadian variation in AD.