Abstract Inflammation plays a critical role in the pathology of acute coronary syndrome (ACS). Matrix metalloproteinases (MMP) – proteolytic enzymes participating in plaque destabilization – are the crucial effectors of proinflammatory mechanisms leading to plaque rupture. Numerous reports have confirmed the significance of these factors both in circulating blood and locally in the plaque. There is, however, a lack of information on the molecular mechanisms leading to these disturbances, and the effect of standard treatment for ACS on these processes. The aim of the study was to assess the gene expression of MMP-2, -9 and TIMP-2, and the effect of standard treatment on the expression of the studied genes. The study was conducted in 32 patients with ACS and 15 healthy subjects (control group). Monocytes were isolated using Rosette-Sep kits. Gene expression of MMP-2, MMP-9 and TIMP-2 was evaluated on days 1 and 5in the studied group and once in controls. Total mRNA was extracted from monocytes and the number of mRNA copies was assessed by QRT-PCR. Monocytes of ACS patients present with significantly higher gene expression of MMP-2, -9 and TIMP-2 compared to healthy controls (0.0915 ±0.037 vs. 0.001 ±0.0002, p<0.01; 0.81±0.279 vs. 0.10±0.057, p<0.05; 0.84±0.140 vs. 0.42±0.126, p<0.05, respectively). After the 5-day standard treatment, a significant decrease in MMP-2 gene expression was observed. Other studied genes did not show relevant changes during the observation period. No significant correlation was found between classical atherosclerosis risk factors and the expression of the studied genes. Monocytes of ACS patients significantly overexpressed MMP-2, MMP-9 and TIMP-2. Five days of standard treatment resulted in down-regulation of the MMP-2 gene. MMP gene overexpression appears to be an independent factor concerning the pathogenesis of ACS.