The kinetics of vesicle formation from hydrotrope/lecithin micelles in the system of lecithin, sodium xylenesulfonate (SXS), and water were studied via the stopped-flow process in conjunction with light scattering; The essential phases in the system are a micellar (L-1) phase and a lamellar liquid-crystalline (LLC) phase. Based upon light scattering and conductance measurements in the L-1 phase, the ratio of SXS to lecithin molecules in the micelles was approximately 1. The results of the stopped-flow process showed the mechanism of formation for the vesicles, which lie in equilibrium between the L-1 and LLC phases, to be by the agglomeration of fragments.