Background: Myocardial remodeling following myocardial infarction (MI) is associated with increased levels of the matrix metalloproteinases (MMPs). Levels of two MMP species, MMP-2 and MMP-9, are increased post-MI and transgenic deletion of these MMPs attenuate post-MI left ventricular (LV) remodeling. This study characterized the spatiotemporal patterns of gene promoter induction for MMP-2 and MMP-9 post-MI. Methods and Results: MI was induced in transgenic mice in which either the MMP-2 or the MMP-9 promoter sequences were fused to the -galactosidase reporter and reporter levels was assayed up to 28 days post-MI. Myocardial localization with respect to cellular sources of MMP-2 and MMP-9 promoter induction were examined. Post-MI, LV diameter increased by 70% (p<0.05), consistent with LV remodeling. -galactosidase staining in the MMP-2 reporter mice was increased by 1 day post-MI, and increased further to 64±6% of LV epicardial area by 7 days (p<0.05). MMP-2 promoter activation occurred in fibroblasts and myofibroblasts in the MI region. In the MMP-9 reporter mice, promoter induction was detected after 3 days post-MI and peaked at 7 days post-MI (53±6%, p<0.05) and was colocalized with inflammatory cells at the peri-infarct region. While MMP-2 promoter activation was similarly distributed in the MI and border regions, activation of the MMP-9 promoter was highest at the border between the MI and remote regions. Conclusions: These unique findings visually demonstrated that activation of the MMP-2 and MMP-9 gene promoters occurs not only in a distinct spatial relation with reference to the MI region but also follows characteristic time-dependent changes post-MI.