Alkyl ethoxy sulfates represent an interesting class of ionic surfactants whose micellar properties depend on the number of ethoxy (EO) groups in their hydrophilic heads. A systematic experimental investigation was carried out on pure, monodisperse samples of dodecyl ethoxy sulfates having one, two, four, and six EO groups. Specifically, the effects of salt concentration (0.1-1.0 M NaCl) and temperature (25-45 degrees C) on micelle shape and size were investigated through dynamic and static light scattering and viscosity measurements. The classical DLVO potential was utilized to quantitatively analyze the effect of intermicellar interactions. In addition, quantitative consistency between the light scattering and viscosity results was demonstrated. It was found that the micelle shape and size of these surfactants are determined through an interplay of electrostatic interactions between the charged sulfate groups and steric interactions between the hydrated EO groups. This interplay can be tuned by varying the number of EO groups, the temperature, or the salt concentration. Specifically, measurements of the average micelle hydrodynamic radius, the average micelle aggregation number, and the micellar solution relative viscosity indicate that, for the surfactants containing one or two EO groups, increasing salt concentration screens electrostatic repulsions between the charged sulfate groups and permits the micelles to undergo one-dimensional growth beyond a threshold salt concentration. In contrast, the micelles formed by the surfactants with the larger heads (containing four or six EO groups) remain spherical over the entire salt concentration and temperature ranges studied. It is proposed that the stronger steric interactions between these larger heads inhibit micellar growth.