Matrix metalloproteinases (MMPs) are a family of enzymes named for their ability to degrade proteins of the extracellular matrix. Here we describe the characterization of a rat monoclonal antibody specifically recognizing one member of this enzyme family, MMP-7. This antibody has been tested for its use in multiple assay types and was shown to be useful for direct enzyme-linked immunosorbent assay (ELISA), Western blotting, immunocytochemistry, and immunohistochemistry of frozen or paraffin-embedded tissues. The antibody has been evaluated for its usefulness with tissues from several different species and, by immunohistochemistry, can detect MMP-7 of human, murine, porcine, and gerbil origin. Immunostaining of MMP-7 in normal tissues or benign tumors of intestinal, breast, and prostatic origin indicates that this protein is normally localized luminally in glandular epithelium. The localization pattern would suggest that in normal or early stage tumors, MMP-7 is most likely not directly involved in extracellular matrix degradation. In contrast, advanced colon tumors show MMP-7 in invading cells at the advancing edge of the tumor.