Field emission properties of undoped chemical vapor deposited diamond and diamondlike carbon films have been measured for a variety of different deposition conditions. The nature and appearance of the damage site after testing, together with the mathematical form of the observed current–voltage relations, are correlated with the conductivity of the film. This is consistent with a model for the overall current which is a combination of conduction mechanisms through the bulk of the film with Fowler–Nordheim tunneling.