BASIC computer programs were written to model the tendency of ionic surfactants to form micelles at various concentrations. A mass-action, multispecies approach involved the use of the hydrophobic effect and the electrical repulsion of the ionic heads, The Poisson-Boltzmann equation was used to model the electrical effects in both planar and spherical coordinates and with and without linearization of the charge density term. In the most elaborate model a modified Boltzmann charge density expression took into account the finite sizes of the ions surrounding the micelle. A "zero surface tension" approach allowed the calculation of the maximum size of the micelle. Calculations focused on the behavior of sodium dodecylsulfate. Micelle formation as a function of ionic strength and surfactant size were satisfactorily modeled. Temperature dependence was not good, and a fitted nonsurface energy term remains unresolved.