A model study of polydisperse micellar solutions formed by ionic amphiphiles in the presence of added salt is proposed. The structural peculiarities of the system are determined by effective potentials including the screened electrostatic and the hardcore interactions. A perturbation procedure is applied to expand the characteristic parameters of the system around a reference system. The basic result is a model size distribution curve that accounts not only for the inherent polydispersity of the system but also includes the interaggregate interactions and the space correlation of the aggregates. Copyright 2000 Academic Press.