Vesicles of different morphologies were found to form in aqueous solutions of the surfactant sodium bis(2-ethylhexyl)sulfosuccinate, AOT, and in binary mixtures composed of AOT with poly(ethylene glycol) and poly(sodium 4-styrenesulfonate). Using electrical conductivity and fluorescence probing, two critical vesicle concentrations, cvc and cac, were determined. These critical aggregation concentrations correspond to different kinds of aggregates, which are easily observed by optical microscopy.