We report the effect of addition of salt KBr on the growth of different sizes of cationic micelles of alkyltrimethyl-ammonium. bromide surfactants in aqueous solution. The surfactants with different hydrophobic tail lengths have been used to vary the size of the micelles. It is found that the effect of salt on the growth of the micelles strongly decreases for the small micelles. We explain these results in terms of counterion condensation, which depends on the size of the micelles. (C) 2002 Elsevier Science B.V. All rights reserved.