Abstract: Objective To investigate neointima hyperplasia and alternation of angiotensin II AT1 receptors after coronary stent implantation. Methods Coronary stent implantation models was established using mini-pigs in which neointima hyperplasia and changes in AT1 receptor mRNA level were detected histologically and by reverse ranscriptional (RT)PCR respectively on days 3, 7, 28, 90 and 180 after the stent implantation. Results The levels of AT1 receptor mRNA showed no obvious changes in the normal vascular tissue at the specified time points. On the 3rd day following stent implantation, the levels of AT1 receptor mRNA increased significantly in the vascular tissues as compared with the adjacent normal vessels, reaching the peak level on day 28. Since day 90 following stent impalntation, AT1 receptor mRNA level began to decline, but still maintained a significantly higher level than that in the normal vessels till day 180. On day 3 after the implantation, the area of the neointima at the implant site showed no obviously changes, which, however, increased significantly as compared with that of the normal vessel and kept proliferating. On day 180, the neointima exhibited obvious hyperplasia at its peak level. Conclusion AT1 receptor mRNA maintains high expression levels in the vascular tissues after stent implantation, which play an important role in sustained neointima hyperplasia.