The use of Type-I-Lyophilized Bovine Collagen became rapidly widespread due to its haemostatic and wound healing effects. It is used widely in the treatment of skin burns and in fields of urology, gynecology and reconstructive surgery. The effects and tissue reactions of Type-I Lyophilized Bovine Collagen were investigated in experimentally traumatized guinea pig livers. Factors studies include necrosis, fibrogenesis, neovascularization, biliary channel proliferation and reticulin formation as well as immunohistochemical fibronectin expression and lysozyme reactive macrophage populations around the traumatized tissues. Compared with the control group the inflammation rate, fibrogenesis and fibronectin reactive values were found to be higher in the experimental group. Since lyophilized collagen shows reparative and haemostatic effects also on the liver tissue, we think that it can be used as an adjuvant material in the liver surgery.