Bone defects in the craniofacial area are a clinical challenge and can be the result of trauma, tumour resection or congenital malformations. The golden standard for reconstruction is autologous bone grafts, but bone may not always be readily available and donor-site morbidity might follow. Alternatives to autologous tissue are sought in the field of tissue engineering, where a range of biomaterials, bone forming cells and growth factors are combined, searching to engineer the missing tissue. The use of bone morphogenetic proteins (BMPs) together with different carriers has been explored ever since Marshall Urist discovered the BMPs in 1965. In this thesis we use BMP-2, together with different carriers in an attempt to reconstruct cranial defects in different species. In paper Ia we look into ectopic bone induction with BMP-2 and heparin/chitosan in a rat model. The resulting bone induction is compared to BMP-2 and type I collagen, and found to be superior in the BMP-2 and heparin/chitosan group. In the following clinical study, paper Ib, BMP-2, heparin/chitosan and titanium mesh are used for the reconstruction of large cranial defects in humans. The patients demonstrate a postoperative inflammatory reaction and week bone formation, and the results are disappointing and discourage the use of heparin/chitosan in a clinical setting. The healing of cranial defects in minipigs with BMP-2 and hyaluronan-based hydrogel is studied in paper II. The defects treated with BMP-2 and hyaluronan-based hydrogel demonstrate 119 percent ossification, indicating complete healing and bone overgrowth to some extent. Animals treated with hydrogel alone show 58 percent ossification and 53 percent ossification in the control group, showing a significant difference in induced bone volumes between the BMP-treated animals and animals treated with hydrogel alone. Bone healing of cranial defects in rats comparing hyaluronic acid hydrogel and type I collagen is studied in paper III. Immunohistochemistry and histomorphometric analysis show ...