Arquad 16-50 (commercial CTAC, cetyltrimethylammonium chloride) (5 mM) with the counterions 3, 4-dichlorobenzoate (5 and 10 mM), 3, 4-dimethylbenzoate (5 and 10 mM) and 3, 5-dichlorosalicylate (5 mM) were studied to compare the effect of concentration of the counterion and its ratio to surfactant concentration (5) on drag reduction, theological behavior, and microstructures. The first four solutions are good drag reducers at different temperature ranges. The 3, 4-dimethylbenzoate system (xi = 1) is effective at 5-40 degreesC and the 3, 4-dichlorobenzoate system (xi = 1) at 20-70 degreesC. Increasing the concentration ratio to xi = 2 increased the upper temperature limit 10 degreesC for each system. The counterion concentration changes affect microstructures in the quiescent state in different ways. The viscoelastic xi = 1 solution of 3, 4-dimethylbenzoate has a microstructure of both vesicles and threads in the quiescent state which probably transform to a threadlike micellar network under sheat However, its ratio of apparent extensional viscosity to sheat viscosity is very low, unusual for a surfactant drag reducer, its xi = 2 solution has typical surfactant drag reducer properties, viscoelastic, high extensional viscosity, and threadlike micellar networks. The xi = 1 solution of 3, 4-Cl-benzoate is like the xi = 2 solution of 3, 4-CH3-benzoate while its xi = 2 solution is nonviscoelastic with vesicles and spherical micelle microstructures in the quiescent state which also probably transform to a network structure in strong shear fields. The only system tested with a counterion having four-substituent groups, 3, 5-dichlorosalicylate, is not effective as a drag reducer, has water-like behavior, and contains very large vesicles.