Objective To investigate the expression and significance of activator protein-1 (AP-1)and matrix metalloproteinases (MMPs) in acute myocardial infarction (AMI) subjects. Methods Immunohistochemical techniques were used to detect the subunit of AP-1 (c-Jun), MMP-2 and MMP-9 in human AMI and normal heart tissue and the expressions of c-Jun and MMPs were measured with computer image analysis system. Results (1) There were expressions of c-Jun, MMP-2 and MMP-9 in normal heart tissue, mainly in myocardial cells and cardiac fibroblasts, and their expressions in AMI myocardial tissues were all significantly higher than those in normal myocardial tissues (P <0.05). (2) The level of MMP-9expression was significantly and positively correlated with c-Jun in AMI heart tissue (r=0.773, P < 0.01).Conclusions The expressions of AP-1 and MMPs increase in human myocardial infarction. These findings suggest that AP-1 transcription activation pathway and MMPs may play an important role in ventricular remodeling of myocardial infarction.