An internal reflectance spectrophotometric technique for the direct study of the infrared spectrum of surface functional groups on carbon is presented. The applicability and limitations of this technique are discussed. The spectra obtained for three different types of carbon; i.e., graphite, carbon black, and activated carbon, are presented. On the basis of interpretation of the spectra for these systems, it is suggested that the predominant surface functional groups on activated carbon are oxygen-containing carbonyl groups. The relative abundance of all oxygen-containing functional groups was found to be a function of both the type of carbon and its pretreatment. © 1969.