Voltammetry with platinum disc microelectrodes has been employed to gain information on the diffusion coefficient, D, of cetyltrimethylammonium bromide, CTABr, aggregates in water, and aqueous solutions of KCI, KBr and KF The dependence of D on surfactant concentration was employed to extract the diffusion coefficient (1.1 x 10(-6) cm(2)/s) at the critical micelle concentration, i.e. where the interaction between the rnicelles is negligible. The dependence of D on the concentration of KCI is explained on the basis of a sphere-to-rod micellar transition. The strong dependence of D on the anion (KBr much greater than KCI > KF) is explained by considering the consequence of anion hydrophobicity on its interactions with the surfactant head-group. (C) 2004 Elsevier Ltd. All rights reserved.