Collagen metabolism in granulating wounds of rat skin was studied with biochemical, isotopic and electron microscopical methods. Deposition of collagen in rat skin wounds was not only the result of an increase in collagen synthesis but it was also caused by a decrease in collagen degradation. Our investigations showed significant differences in the collagen turnover at different times of wound healing. Decreased collagen catabolism at the early stages of wound healing contributed decisively to collagen accumulation in the wound area. At later stages, during wound contraction and remodelling of the scar, the rate of collagen degradation rose. The above-mentioned results are discussed in the context of general criteria of scar formation.