Abstract： Background Endovascular stent-graft treatment has emerged as an altemative for patients with type B aortic dissection (AD),either at acute or chronic phase,in selected patients.This study aimed to investigate the results of endovascular stent-graft repair for acute and chronic type BAD.Methods From May 2002 to July 2007,67 patients with type BAD were treated by endovascular stent-graft placement.There were 32 patients in the acute phase (PAD group) and 35 patients in the chronic phase (CAD group).The patients were followed up from 1 to 65 months (average,17±16 months).The immediate and follow-up clinical outcomes were documented and compared between the 2 groups.Results Placement of endovascular stent-grafts across the primary entry tears was technically successful in all 67 patients.Compared with patients in the CAD group,those in the AAD group had higher percentages of pleural effusion (15.6% vs 0,P=0.02) and visceral/leg ischemia (21.9% vs 2.9%,P=0.02).Procedure related complications,including endoleak and post-implantation syndrome occurred more frequently in PAD group than in CAD group (21.9% vs 2.9% and 31.3% vs 8.6%,respectively;P=0.02 and P=0.02).Kaplan-Meier analysis showed no significant difference in survival rate at 4 years between the 2 groups (86.4% vs 92.3%,P=0.42 by Log-rank test).But the 4-year event-free survival rate was higher in patients with chronic dissection than in patients with acute dissection (96.2% vs 73.9%;P=0.02 by Log-rank test).Conclusions Endovascular repair with stent-graft was safe and effective for the treatment of both acute and chronic type BAD.However,both immediate and long term major complications occurred more frequently in patients with acute dissection than in those with chronic dissection.