Theoretical and technical aspects of coupled multi-angle light scattering (MALLS), refractometric and viscosimetric detectors for SEC applications are considered. Absolute mass, radius of gyration and reduced viscosity distributions are obtained in this configuration, and an example application is made to characterizing water soluble polyelectrolytes. This characterization also includes illustrations of polymer form factors, interparticle structure factors, the failure of 'universal calibration', and a comparison of low angle light scattering (LALLS) and MALLS. Finally, a summary of sources of systematic and random errors is given, with estimates of the effects of each source on the characterization parameters.Polydispersity has long been the bane of macromolecular characterization. Different techniques applied to unfractionated batches' of polymer, such as static and dynamic light scattering, osmotic pressure and viscometry, all yield different averages over the mass distribution for the quantities they measure. The averages are often difficult to interpret and compare to each other, and contain no direct information about the width, shape, or peculiarities of the mass distribution.It is hence desirable that fractionation techniques, such as size exclusion chromatography (SEC), be able to provide an absolute determination of the mass distribution, from which all the mass moments can be computed, and, simultaneously, be able to measure as many useful , associated, mass-dependent properties, X(M) as possible. These latter properties may include the root mean square radius of gyration Rg (=l/2 > w here is the mean square radius of gyration), intrinsic viscosity [η], diffusion coefficient, specific conductivity, etc. Over the past fifty years a large body of theoretical and empirical knowledge has been built up concerning the physical relationship between polymer structure, dimensions, interactions and hydrodynamics, as revealed by such properties. Many