The effect of KBr on the size, shape and microviscosity of CTAB micelles has been investigated by means of laser light scattering (LLS), H-1 NMR measurements and fluorescence probe. The data obtained from the various techniques are quantitatively in agreement. The R-h of micelles in 0.01 mol . L-1 CTAB solution increases from 3.5 nm to 43 nm and R-g increases to 89 nm with addition of KBr salt. In this process, both the microviscosity and molecular weight of micelles M-w have noticeable increases, too. The rod-like micelles are formed at 0.1 mol . L-1 KBr and the worm-like micelles are formed at above 0.2 mol . L-1 KBr.