In this work, parylene-C is exposed to the effluent from a microwave ammonia plasma with a goal of producing primary amine groups on the parylene-C. These amine groups are desired as sites for the attachment of various biomolecules that will influence the biocompatibility of the parylene-C. Ammonia plasma treatment is an effective approach for creating amine species on polymers. In this work, attenuated total reflectance infrared spectroscopy studies showed that no primary amine groups resulted from this treatment of parylene-C. Instead, reactive nitrogen-bearing radicals from the plasma appear to have been complexed by chlorine in the polymer. The formation of these complexes scavenged nitrogen-bearing radicals from the plasma and prevented the formation of nitrogenous species, such as the desired primary amines, on the parylene-C. These results are consistent with results of ammonia plasma treatment of other chlorinated polymers and suggest that alternative approaches are required to create nitrogen-bearing species on parylene-C. (c) 2005 American Vacuum Society.