Objective To study the expression of interleukin-1β in aortic dissections and aneurysms. Methods Aortic specimens were obtained from patients with type Ⅰ thoracic aortic dissection (11 cases),ascending thoracic aortic aneurysms (10 cases),and healthy organ donors (7 cases).Expression of interleukin-1β,matrix metalloproteinase-9,and signal transduction factors phospho-p38 and phospho-JNK were detected by real time RT-PCR,Western blot,and immunohistochemistry,respectively.TUNEL staining was performed to detect apoptosis of media cells. Results Apoptosis in the media of thoracic aortic dissection and ascending thoracic aortic aneurysms was dramatically higher than control group.Expression of interleukin-1β gradually increased in an order of control group,thoracic aortic dissection to ascending thoracic aortic aneurysms ( P ＜ 0.01,respectively).Expression of matrix metalloproteinase-9significantly increased in the media of thoracic aortic dissection and ascending thoracic aortic aneurysms compared with control group (P ＜ 0.01,respectively).There were positive correlations between interleukin1 β and matrix metalloproteinase-9,interleukin-1β and phospho-p38 in thoracic aortic dissection ( P ＜ 0.01,respectively),interleukin-1β and apoptosis in ascending thoracic aortic aneurysms (P ＜ 0.01 ).Conclusions Interleukin-1β and interferon-γ might effect the formation of thoracic aortic dissection and ascending thoracic aortic aneurysms possibly through the up-regulation of matrix metalloproteinase-9 and apoptosis of media cells in humans.