A frontal chromatographic method for the investigation of self-associating patterns has been developed and applied to the micellization of surfactants, bile salts, and drugs. The chromatogram on Sephadex G-10 gels, which have too small pores to include any aggregate species including dimer, provides the monomer (intermicellar) concentration of solute as a function of the total concentration. From analysis of the dependence of the monomer concentration on the total concentration by multiple equilibrium model of self-association, we can determine weight- and number-average aggregation numbers as a function of the total concentration. This data allows us to estimate micelle size distributions on the basis of an appropriate model or molecular thermodynamic theory of micellization. The critical micelle concentration can be defined theoretically as the total concentration where the third derivative of monomer concentration with respect to the total concentration is null. The dimers of surfactants are generally present, although the dimerization constants are very small. Phase separation model and mass action model for micellization are not rigorously valid even for surfactants. Micelles of spheres and rods coexist for penta- and hexaethylene glycol dodecyl ethers. In the self-association of bile salts and drugs, dimers and oligomers are important aggregates, so that they self-associate less critically than surfactants. Bile salts and their zwitterionic derivatives form stable multiples of dimer. Derivative chromatograms are used to distinguish between aggregation patterns and to estimate the dimerization constant. Chemical structures of solutes are closely related with aggregation patterns.