Abstract—Crevicular fluid (CF) samples were collected by paper strips from healthy and diseased sites. The molecular distribution of fibrin and fibronectin in CF and plasma samples was investigated using SDS‐polyacrylamide gel electrophoresis and specific immunoglobulins. Intact fibrin was found in all CF samples. In addition several bands with both lower and higher molecular weights than intact fibrin were seen. These bands were not present in the plasma samples. The low molecular weight bands are suggested to represent degradation products of fibrin. The high molecular bands could be fibrin‐fibronectin complexes or fragments of large fibrin polymers. Fibronectin degradation products, but not intact fibronectin, were seen in both healthy and diseased sa