We are studying the possibility of quantitating soluble collageneous proteins in biological fluids using an enzyme affinity assay. This assay is based on the interaction of fibronectin with unwound, denatured collagen. Quantitation is done using enzyme labeled anti-fibronectin. Samples are treated before assay in order to maximize denaturation of both collagen and endogenous fibronectin. The assay is to be used to quantitate collagen in blood and other fluids in conditions where protein bound hydroxyproline have previously been analyzed and found increased. Identification of the collagen assayed will be attempted using affinity chromatography on insolubilized fibronectin and subsequent polyacrylamide gel electrophoresis. Alternatively, identification of collagen-like proteins after electrophoresis is done using labeled fibronectin.