The aim of this study was to investigate if the serum concentrations of antigens related to basement membrane components and to the interstitial type III collagen reflect the sequential and transitional synthesis of basement membranes and of type III collagen in wound granulation tissue. The aminoterminal propeptide of type III collagen, the 7S domain of type IV collagen and the P1 fragment of laminin were determined in 11, 10 and 6 patients, respectively, during wound healing following intraabdominal surgery. No change was observed in the type III propeptide level at the first postoperative day. During further follow-up (mean 71 days, range 21-155 days), the propeptide levels showed a transitional increase, with a maximum at day 10. A sequential pattern was observed in the increase of the serum concentrations, as the maximum increase of the basement related antigens in serum occurred within the first 7 postoperative days. This is in accordance with observations of an early formation of basement membranes in blood vessels, preceding deposition of interstitial collagens in granulation tissue. The results support the assumption that the serum concentrations of connective tissue related antigens may be valuable markers of wound healing in man.