Aim To investigate the role of peroxisome proliferator activated receptor-γ (PPAR-γ) in the regulation of matrix metalloproteinases (MMP-9) and tissue inhibitor of metalloproteinase (TIMP-1) expression by peripheral blood monocyte derived macrophages (MDM) in acute coronary syndrome (ACS) patients. Methods MDM were from patients with ACS and controls have been assigned to different subgroups and incubated by different concentrations of rosiglitazone. The concentrations of MMP-9 and TIMP-1 in the supernate of MDM and the expression strength of PPAR-γ,MMP-9 and TIMP-1 mRNA in MDM were analysed and compared between ACS group and control group,and among the different concentrations of rosiglitazone intervention subgroups. Results After rosiglitazone interventing,either in ACS group or in control group,PPAR-γ mRNA expression were significantly upward,and there were a positive correlation between the expression strength and rosiglitazone intervention concentration; both the MMP-9 concentration in the supernate and the expression strength of MMP-9 mRNA were descended,and there were negative correlation between the extent of its descent in the ACS group and rosiglitazone concentration. There was no significant change in TIMP-1 concentration in the supernate of MDM and TIMP-1mRNA expression after rosiglitazone interventing. Conclusion MDM had endogenous PPAR-γ receptor,and it could be activated by rosiglitazone. Rosiglitazone intervention significantly increased the expression of PPAR-γ of MDM,reduced the expression of MMP-9,particularly in the ACS group. TIMP-1 expression was not affected. There may be impact of stablizing atherosclerotic plaque.