The Matrix metalloproteinase-9 functional promoter polymorphism 1562C>T may be considered an important genetic determinant of early-onset coronary artery disease (ECAD). In this study, association between MMP-9 1562C>T allele with plasma MMP-9 activity, homocysteine and lipid-lipoproteins level and ECAD in Iranian subjects was investigated. This case-control study consisted of 53 ECAD patients (age < 55 years) and unrelated late-onsets CAD (age>70 years) who angiographically had at least 50% stenosis. MMP-9 1562C>T polymorphism was detected by PCRRFLP, plasma MMP-9 activity, serum lipid and homocysteine levels were determined by gelatin gel zymography, enzyme assay and by HPLC, respectively. The presence of MMP-9 1562C>T allele was found to be associated with ECAD (OR=3.2, P=0.001). The ECAD patients with MMP-9 1562C>T allele had higher MMP-9 activity (P=0.001), LDL-C (P=0.045), TC (P=0.02) and homocysteine (P=0.01) levels than the LCAD subjects. MMP-9 1562C>T allele is a risk factor for ECAD. The carriers of this allele have high levels of MMP-9 activity, LDL-C, TC and homocysteine (P=0.01), thus, are more likely to develop myocardial infarction and CAD at young age (less than 55 years).