The growth and structure of the aqueous micellar solutions of a surface active ionic liquid, 1-hexadecyl-3-methylimidazolium bromide (C(16)mimBr), in the presence of an organic salt sodium tosylate (NaTos), were investigated by rheological measurements and freeze-fracture transmission electron microscopy at room temperature (298 K). As in some conventional ionic surfactant/salt aqueous systems, wormlike micelles and network structures could be formed in the C(16)mimBr/NaTos aqueous solutions, according to measurements of the zero-shear viscosity, the entanglement length, the average contour length, as well as application of the Cox-Merz empirical rule and Cole-Cole plots. FF-TEM images further confirmed that wormlike micelles were formed in these aqueous solutions. The wormlike micelles presented here would expand potential applications of ionic liquids in home care products, oilfield stimulation fluids, and nanobiotechnology. (C) 2007 Elsevier Inc. All rights reserved.