Objective: To explored the significance of the Interleukin-18 (IL-18)/Interleukin-10 (IL-10) ratio in patients with in stent restenosis (ISR) after percutaneous coronary intervention(PCI).Methods: 108 patients with SA, 46 with UA, 67 with ISR were enrolled into the prospective study.IL-18, IL-10 and lymphocyte subsets were measured in blood samples collected before and 24 h and 6 months after the procedure.Results: IL-18/IL-10 ratio increased significantly in each group with the peak value at 24 h, but the baseline values had no significant difference.