In this paper we first describe the basic idea of adhesion and various methods for measuring adhesion. We then discuss the various state-of-the-art techniques for the improvement of the adhesion between diamond films and substrates. The techniques discussed are categorized into two main types: (a) those which reduce internal stress and (b) those which increase the ideal or basic adhesion itself. Techniques in category (a) include forming a composition gradient layer on top of an insert substrate surface to reduce the detrimental effect caused by the difference in thermal expansion with diamond, and/or the use of insert substrates themselves having a smaller difference in thermal expansion with diamond. Techniques in category (b) include modification of cemented carbide substrates so as to reduce the detrimental effect caused by Co and the increase of the mechanical interlocking effect using a special etching process.