Syntheses, adsorption, and aggregation properties of two novel double-chain anionic sulfoglutaconate surfactants are described. These compounds are similar to the more common sulfosuccinates, such as Aerosol-OT (see Parts I and II of this study, Nave et al. Langmuir 2000, 16, 8733-8748), but with a modified hydrophilic moiety bearing one extra -CH2- spacer. For comparison purposes, two related linear n-hexyl- and branched 2-ethylhexyl- hydrophobic groups were used to form the surfactants, which are denoted di-C6GLU and AOTGLU. The planar air-aqueous solution surface was characterized by drop volume tensiometry, whereas small-angle neutron scattering and spinning-drop tensiometry were used to study microemulsions and oil-water interfaces. Dilute binary surfactant water and ternary water-in-oil microemulsion phase behavior is also described. In terms of molecular packing both glutaconate and sulfosuccinate systems are found to be very similar, showing the minor role of the headgroup compared to larger effects of the tail structure, as noted before in Parts I and II. Interestingly, the AOTGLU proved to be even more efficient than normal AOT in terms of its capacity to microemulsify water in heptane. The results point to subtle effects of hydrophilic group structure on physicochemical properties of these AOT-type surfactants, especially in microemulsions.