Chemically vapor deposited (CVD) diamond films have been deposited by a microwave enhanced deposition process on metal substrates including titanium, tungsten, molybdenum, and copper. Boundary reaction layers formed at the interface during the growth of the CVD diamond films have been investigated for each of these systems. In these studies, the interface has been exposed by mechanically deforming the metal substrate to cause film delamination. Where the diamond film has adhered to the substrate through the growth process, delamination procedures have been carried out under controlled conditions in order to preserve the integrity of the interfacial species. The exposed interfaces were characterized by x-ray photoelectron spectroscopy, scanning Auger microscopy, secondary electron microscopy, and Raman microprobe spectroscopy. Reaction layers composed of carbides and oxides of the native metal were detected at the interfaces of titanium, tungsten, and molybdenum while only traces of carbon and oxygen were detected at the diamond/copper interface. We believe that both the chemical composition and morphology of the interface influence the adhesive properties of the diamond coating. Correlated investigations of the interfacial surfaces reveal that fracture of the diamond/metal interface occurs discretely at the diamond nucleation plane or within a reaction layer near the diamond interface.