Cellulose sponges were cut into two pieces and fibrin sealant was applied to the opposing surfaces, which were held together with sutures. In each rat two sets of sponges, one with and one without fibrin sealant, were implanted subcutaneously for 10 days. The tensile strength and energy absorption of the granulation tissue bridging the incision of the sponges were not influenced by the fibrin sealant. The formation of collagen in fibrin-sealed sponges did not differ from that in ordinary sponges. The results indicated that fibrin sealant does not influence the collagen formation and the mechanical strength after 10 days of healing. At this time the tissue possesses pronounced mechanical strength. The initial strength of sealed sponges possessed considerable mechanical strength (maximum stress 25% and failure energy 12% compared to values achieved after 10 days of implantation). This indicates that the sealant gives mechanical strength in the first days of healing, where the granulation tissue itself only provides minimal strength.