The pore-size distribution (PSD) of a liquid-saturated porous medium can be determined by inverse size-exclusion chromatography (ISEC) under suitable conditions. To quantify the limitations of longitudinal dispersion, intraparticle diffusion, and adsorption, we present a mathematical model for chromatographic procedures with polydisperse solutes. Results are applicable to either inverse or ordinary SEC. The conventional ISEC procedure with monodisperse polymer standards is a special case of the general development. Chromatographic responses for polydisperse solutes permit determination of the pore-size distribution by a deconvolution procedure if adsorption is negligible.