A flow microcalorimeter system was assembled and is being used in a thermodynamic study of surfactant systems as part of the ERDA enhanced oil recovery program. Enthalpies of dilution and demicellization of sodium dodecyl sulfate were measured over a temperature range of 20 to 35/sup 0/C. This surfactant was also studied with cosurfactant and salt backgrounds. The critical micelle concentrations (cmc) were determined and are in excellent agreement with those in the literature. Studies below the cmc suggest the possible formation of a dimer. 17 tables, 9 figures.