Objective:To investigate the expression and significance of p38 mitogenactivated protein kinase (MAPK) in autogenous vein graft. Methods: Autogenous vein graft model was established by transplanting the right jugular vein to infrarenal abdominal aorta in 80 Wistar rats. Ten vein graft samples were harvested 6 hours, 24 hours, 3 days, 7 days, 2 weeks, 4 weeks, 6 weeks and 8 weeks after surgery,respectively. Reverse transcriptionPCR and in situ hybridization,Western blot and immunohistochemistry methods were used to detect the expression of protein and phosphorylation protein of p38 and p38mRNA. Results:The expression of p38 mRNA increased 6 hours after surgery and reached the peak on the second week after surgery (59%±26%）,and significantly higher than that on 4,6,8 weeks( P<0.01 vs.), Expression of p38 detected by Western blot reached to the peak on 2 to 4 weeks, and decreased significantly to 1/4 to 1/2fold on 8 weeks after surgery. The positive cells were mostly located in the vascular smooth muscle cells(VSMCs) in the media and/or intimal hyperplasia of vein graft. Conclusions: The activation of p38 MAPK system in intimal hyperplasia and vascular remodeling after vein graft may become a new target of the therapy for stenosis or obliteration of vein graft.