An adhesive bond is a sandwich structure that has various zones within it as shown in Fig. 1. The physical and chemical properties of these various zones determine the bond strength and the durability of the bond. I hope that I'll be able to shed some light on the real properties of the interface rather than schematic properties as shown in Fig. 1 and relate the physical and chemical properties to the resultant bond strength. I will, therefore, discuss something about the oxide, the topography of the surface after it's been prepared for bonding , the thickness of the oxide, the interface , the primer and the adhesive in an actual fracture surface. The dotted line in Fig. 1 represents a hypothetical fracture line and, in fact, we find that failure does occur in all of these regions designated by the dashed line. The bond fails as the weakest regions fail.