Resonance light-scattering measurements have been employed to investigate the solute species present in acidic aqueous media for some 14 sulfonated porphyrins. The results confirm that the anomalous absorption band in the Soret region reported for several of these porphyrins arises from the formation of extended aggregates of electronically coupled chromophores and illustrate the sensitivity and specificity of this unconventional light-scattering method.