Biologic and non-biologic materials clinically used as hemostyptica, as vascular prostheses, or as temporary skin substitutes were implanted to the chick chorioallantoic membrane (CAM) during days 9-14 of incubation. The histological study revealed an intact CAM after application of cellulose gauze (Tabotamp). The fibrin tissue adhesive (Tissucol), the collagen sponge (Tachotop), or the gelatin sponge (Gelfoam) induced different amounts of connective tissue. Some fibroblasts were about to grow into the fibrin adhesive. Fibroblasts and capillaries filled the interstices of the collagen sponge poorly, and in the case of the gelatin sponge markedly. Neutrophils and giant cells of the foreign body type occurred more often in the gelatin sponge than in the collagen sponge. With regard to the non-biologic materials, expanded polytetrafluorethylene induced squamous metaplasia of the chorionic epithelium. Dacron caused ulceration with the onset of connective tissue ingrowth, based on a reaction of giant cells of the foreign body type. Polyurethane foam (SYSpur-derm) showed bleeding into the implant due to spikes of the material. Eosinophilic granulocytes were absent in all materials studied. The results are related to different clinical findings. The correlation allows consideration of the CAM as an in vivo model in screening materials for their biocompatibility and their connective tissue reaction.