This review article demonstrates that the light scattering technique provides important structural information of the following macromolecular assemblies, polymer living anions in a non-polar solvent, amphiphilic telechelic polymer and block copolymers in aqueous solution, and a thermally denatured double-helical polysaccharide aggregated during renaturation. To get accurate information from light scattering data, however, we have to analyze the data using proper theoretical tools, which are briefly explained in this article. The structural information of these macromolecular assemblies assists us in understanding, e.g., the kinetics of living anionic polymerization and gelation.