For rapid development of initial solvent extraction processes, knowledge of the solubility and partition behavior of surfactants and solubility enhancers is required. Unfortunately, experimental solubility data for many common surfactants and solubility enhancers in aqueous and organic solvents have not been reported. There are also few references to the partitioning behavior of these additives between water and common extraction solvents. In this paper, the solubility and partition coefficients were measured at 293 K for a range of additives in solvent systems of varying polarities and classes:  ethyl acetate, isobutyl alcohol, toluene, methyl ethyl ketone, methyl tert-butyl ether, and 0.2 mol·L-1 potassium phosphate buffer (pH 7). The additives chosen were based on common usage and represent a cross-section of the surfactant classes:  UCON LB-625, P2000, Triton X-100, sodium dodecyl sulfate (SDS), Tween 20, Tween 80, hexadecyltrimethylammonium bromide (CTAB), ammonium sulfate, and methyl-β-cyclodextrin. The partition behavior of these additives (except Tween 20) was also investigated. The effect of ionic strength, pH, and cosolvents on the partition coefficient was also determined to provide a database for surfactant and solubility enhancer behavior in order to allow for rapid optimization of initial extraction processes. The solubility results showed that the antifoams were extremely soluble in the organic solvents but had limited solubility in water. The nonionic surfactants were soluble in all solvents tested. The anionic surfactant was soluble in all solvents tested, with the exception of toluene. The cationic surfactant and ammonium sulfate had limited solubility in most solvents. The methyl-β-cyclodextrin had varying degrees of solubility depending on polarity. The partition results can largely be predicted from the solubility data, with the exception of the nonionic surfactants. For all of the compounds that partitioned, the behavior could also be predicted based on solvent polarity, with larger partition coefficients for the more polar solvents. These data can be used to design initial extraction processes containing these additives and, by analogy, for other related additives as well.