Linear and nonlinear predictive models are derived for a data set of 162 nonionic surfactants. The descriptors in the derived models relate to the molecular shape and size and to the presence of heteroatoms participating in donor-acceptor and dipole-dipole interactions. Steric hindrance in the hydrophobic area also plays an important role in micellization. The derived linear and nonlinear QSPR models could be useful to predict the CMCs of broad classes of nonionic surfactants.