Fibronectin, an adhesion protein found in blood and tissues, is an important factor in wound repair. Recently, we began studies using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting to compare fibronectin in the fluid of normal and chronic wounds. We found similar fibronectin profiles in suction blister fluid (2 normal volunteers) and mastectomy fluid (5 patients). There was primarily an intact 250 kilodalton fibronectin subunit and in addition some higher molecular mass fibronectin-containing complexes. On the other hand, fibronectin in diabetic ulcer wound fluid (2 patients) was partially degraded, and there was no intact fibronectin in stasis ulcer wound fluid (2 patients). The most prominent degradation products were 93 and 125 kilodalton polypeptides. When intact fibronectin was added back to stasis ulcer wound fluid, fragmentation occurred within 15 minutes at 37 degrees C indicating the presence of protease activity in the wound fluid.