The nucleophilic sulfonation of decyl halides and benzyl halides was carried out at 298.2 K in batches in o/w microemulsions and emulsions formed with the two-tailed cationic surfactants dioctyldimethylammomum chloride, R2(Me)2N +Cl-, or bromide, R2(Me) 2N+Br-. The effects of mixing, surfactant concentration and counterion, and reactant concentrations on the conversion of the halide were investigated. At the concentrations employed, phase separation occurred in most of the samples. Mixing did not affect the sulfonation of decyl halides, while it governed the sulfonation rate of benzyl halides. Chloride as the surfactant counterion reacted with the bromide and iodide halides to form an intermediate, decyl chloride, and a side product, benzyl chloride. At a fixed time, the conversion to the final product versus surfactant concentration displayed a broad maximum. The tendency of sodium decyl sulfonate to remain at the interface resulted in lower conversion with increasing decyl halide concentration, while the formation of a separate benzyl halide phase produced the same effect. Increasing the mole ratio sodium sulfite/halide reactant increased the conversion to the final product in a manner that supports the mechanisms of ion exchange with the surfactant counterions and a second order nucleophilic substitution.