The monomer-aggregate exchange rate in self-assembled dialkyl chain cationic-nonionic mixed surfactant aggregates has been studied using small-angle neutron scattering, SANS, and a stopped-flow apparatus. SANS was used to follow the evolution of the structure with time of an equimolar mixture of the dialkyl chain cationic surfactant dihexadecyl dimethyl ammonium bromide, DRDAB, in D2O with the nonionic surfactant dodecaethylene monododecyl ether, C12E12, in D2O at a solution concentration of 1.5 mM. With increasing time, the bilamellar vesicle structure, blv, of DHDAB and the globular micellar structure, L-1, of C12E12 evolved to a lamellar (L-beta or L-alpha/micellar (L-1) coexistence. Measurements were made for the isotopically labeled combinations of hydrogeneous DHDAB (h-DHDAB) and alkyl chain deuterium-labeled C12E12 (d-C12E12) in D2O such that the lamellar contribution is the predominantly visible contribution to the scattering. From the variation (decrease) in the scattering intensity with time (measured at a scattering vector of similar to 0.014 angstrom(-1)), a characteristic time was measured at 32 degrees C (T < L-beta/L-alpha transition temperature) and at 46 degrees C (T > L-beta/L-alpha. The characteristic time was similar to 130 min and a few seconds respectively, indicating a dramatic change in the monomer/aggregate exchange rate between the solid-like L-beta and fluid-like L-alpha phases. The characteristic time of similar to 130 min in the L-beta phase is indicative of a slow monomer aggregate exchange rate and is consistent with the slow kinetics of adsorption of DHDAB and DHDAB/nonionic surfactant mixtures observed at the air-water interface. This slow adsorption kinetics was assumed to arise from near-surface depletion effects associated with slow monomer/aggregate exchange rates, and these results support and reinforce that hypothesis.