The aqueous microemulsion system consisting of the fluorinated surfactant tetraethylammonium perfluorooctylsulfonate (TEAFOS) and the fluorinated oil H-1-perfluorohexane (PFH) has been investigated using. the pulsed field gradient NMR self-diffusion method on both H-1 and F-19. Neat TEAFOS(aq) builds threadlike micelles from rather low surfactant concentrations up to ca. 80 mmol kg(-1). The addition of PFH to TEAFOS(aq) solutions induces a transition from threadlike micelles to spherical micelles solubilizing the oil. In this paper, information from the self-diffusion coefficients of oil (PFH), surfactant counterion (TEA(+)), surfactant ion (FOS-), and water (HDO) during the transition is presented.