Experiments for determining the adhesion strength between TiN or Al coatings and high speed steel (HSS) have been performed by using the three-point bend test and a modified shear test. Sample preparation is easier for the modified shear test; however, the interpretation of the results is more complicated. The three-point bend test yields fracture mechanics data such as the interface fracture energy, G(c),the fracture toughness, K-c. A copper sublayer with weak adhesion has been used as a notch which initiates crack propagation at the coating/substrate interface. The fracture mechanics tests were complemented by scratch tests and microindenter measurements. The effects of coating thickness and of oxygen contaminations in the sputtergas atmosphere during deposition of TW coatings, or of substrate sputter cleaning on the adhesion of Al coatings has been investigated with several sets of samples after an identical pretreatment. Interface fracture toughness values are in the range of 1.3 MN m(-3/2) for TiN coatings and 0.75 to 1.75 MN m(-3/2) for Al coatings.