Micellization behavior of a variety of nonionic, anionic, and cationic surfactants is analyzed using two different approaches. In one of them, the optimal micelle size approach, the contribution of only the most populous micelle size is considered in the calculation of the aggregation number, critical micelle concentration, etc. The second approach involves the size distribution of the micelles. Both approaches are found to be equally satisfactory in predicting the experimentally observed aggregation numbers and critical micelle concentrations of pure surfactants. In analyzing the effect of salt on the micellar size, both models predict that the aggregation number increases with increasing salt concentration. Assuming that the spheroidal—rod transition in the micellar shape occurs when the ratio of anisotropy of micellar aggregates equals 2.0, a threshold salt concentration for the above transition is calculated for both anionic and cationic surfactants. In agreement with the experimentally observed trends, it is shown that this threshold concentration decreases with the decreasing size of the head group and with the increasing degree of counterion binding to the micellar surface. However, the agreement is largely qualitative with either of the models. Additives such as medium- and longer-chain-length alcohols decrease the critical micelle concentration of a wide variety of surfactants and this depression is larger for longer alcohols. Again, the above predictions of both approaches are similar to those observed experimentally, and it is shown that either of the two models is equally satisfactory in providing quantitative agreement with the available experimental data. The size distribution model provides values that are, in general, somewhat lower than those of the experimental data, whereas the optimum size approach yields results that are, in general, slightly higher than the experimental ones.