The work conducted at the National Institute of Standards and Technology over the last 7 years on the systematic synthesis and assessment of fundamental knowledge on low-energy electron interactions with plasma processing gases is briefly summarized and discussed. This work deals mostly with the primary electron interaction processes. Assessed data on electron collision cross sections and rate coefficients are discussed and their multiple value is indicated. Data needs are identified for electron interactions with ground-state, excited, and transient species, and for electron energy losses. It is indicated that the currently limited knowledge on electron reactions at surfaces and interfaces can be aided by related existing knowledge on electron interactions in dense gases, liquids, clusters, and molecular layers on cold surfaces. Published by Elsevier Science B.V.