The kinetics of the basic hydrolysis of N-methyl-N-nitroso-p-toluenesulfonamide were studied in media containing sodium dodecyl sulfate (SDS) or tetradecyltrimethylammonium bromide (TTABr) micelles and beta-cyclodextrin (CD). Under the experimental conditions, [NaOH] = 0.17 M, all CD will have been deprotonated; thus, binding constants apply to the CD anion. The results have been interpreted in terms of a pseudophase model that takes into account the formation of both CD-surfactant and CD-substrate complexes and also, for TTABr systems, the exchange of Br- and OH- ions between the micellar and aqueous pseudophases. The presence of CD has no effect on existing SDS or TTABr micelles but raises the cmc : complexation of surfactant by cyclodextrin makes the cmc dependent on CD concentration because the cmc is now the sum of the concentrations of free and complexed surfactant when micelles begin to form; increasing [CD] reduces the former quantity but increases the latter to a greater extent. At surfactant concentrations above the cmc, competition between the micellization and complexation processes leads to the existence of a significant concentration of free cyclodextrin.