Plastics are bonded in many applications to a wide variety of materials, including metals, ceramics and the same or other plastics. The adhesive may be the plastic, such as bonding metal to metal. Failure of the adhesive bond may be due to (1) formulation additives migrating into the adhesive bond, (2) extraneous foreign contaminants, (3) environmental conditions such as water and temperature, (4) physical effects of the bonded materials such as coating thickness. Differences in coefficient of thermal expansion, such as metal and plastic, may stress the adhesive bond as temperature changes. Analytical methods to identify the cause of failure involving formulation additives and contaminants are infrared spectroscopy and thermal desorption gas chromatography/mass spectroscopy at and below the surface. Case studies and examples will illustrate a variety of adhesion failures.