To investigate the expression and significance of activator protein-1 (AP-1) and matrix metalloproteinases (MMPs) in acute myocardial infarction (AMI) subjects.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.(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 (P0.05). (2) The level of MMP-9 expression was significantly and positively correlated with c-Jun in AMI heart tissue (r = 0.773, P0.01).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.