The expression of two matrix metalloproteases (MMPs), 72 kDa gelatinase (MMP-2) and 92 kDa gelatinase (MMP-9), was studied in suction blister fluids and serum using a zymographic method. Both of the enzymes were detectable in blister fluid and serum, but their expression varied. The MMP-2 levels in serum were only about half of the levels in blister fluid, while the level of MMP-9 was about the same in both serum and blister fluid. The overall level of MMP-2 in serum was much lower than the level of MMP-9 which was possibly derived from inflammatory cells. In subjects aged from 20 to 86 years, no marked changes were seen in the serum or blister fluid gelatinases. Interestingly, body site affected the level of MMP-9. The lowest level was recorded in fluid from blisters on the lower leg, in which the level was only about 19% of the level in fluid from blisters on the abdomen. The levels of MMP-2 and MMP-9 were not decreased by pharmacological doses of systemic prednisone or isotretinoin, which indicates that systemic glucocorticoid or retinoid treatment does not affect the basal levels of MMP-2 and MMP-9.