Matrix metalloproteinases (MMPs) are involved in remodelling extracellular matrix. Gelatinase B (MMP-9) is an inducible 92 kDa MMP expressed by neutrophils, microglia, and endothelial cells. Gelatinase A (MMP-2) is a 72 kDa MMP, constitutively expressed in brain. Elevated MMP activity has been linked to various pathologic conditions, and the therapeutic benefit of MMP inhibitors is under study in a few experimental models. Using gelatin zymography, we have compared activities of these MMPs in infarcted and matched non-infarcted cerebral tissue from eight subjects dying at intervals of less than 2 h to several years after a stroke. Gelatinase B activity was markedly elevated in the infarcted tissue at two days post-infarction, and remained elevated in cases dying months after the event. Increases in gelatinase A activity were subtle at 2-5 days; they were marked and significant in cases dying at 4 months and later. The findings indicate distinct temporal profiles of post-ischemic gelatinase activity in human brain, with earlier but equally persistent elevation in gelatinase B when compared to gelatinase A.