The mRNA localizations of gelatinase A(MMP-2) and type I carcinoma and non-neoplastic fibrous granulation tissue were compared. By in situ hybridization, gelatinase A was shown to be expressed in fibroblasts not only in cancer stroma but also in the "reactive fibrosis zone," which surrounds the invasive margin of cancer. In most cases, no accentuation of gelatinase A expression was observed in the invasive margin. This localization pattern of gelatinase A was essentially the same as that of type I procollagen. In gastric cancer associated with deep ulceration, gelatinase A was more abundantly expressed in fibroblastic cells in granulation tissue of the ulcer base than in cancer stroma. The same situation was found in non-neoplastic fibrous granulation tissue, in which fibroblasts abundantly expressed mRNAs for both gelatinase A and type I collagen. Scar tissue (old fibrotic lesion) showed diminished expression of mRNAs for both gelatinase A and type I procollagen. The localization patterns suggest another function of gelatinase A in cancer tissue as a turnover enzyme of the extracellular matrix.