The determination of molecular weight (M) and molecular weight distribution (MD) of heparins by a novel approach, consisting of a high performance size exclusion chromatography (HP-SEC) combined with a triple detector array (TDA) is described. HP-SEC/TDA permits the evaluation of MD of polymeric samples through a combined and simultaneous action of three on-line detectors, right-angle laser light scattering (RALLS), refractometer (RI), and viscometer. The method does not require any chromatographic column calibration, thus overcoming also the difficulty to obtain adequate reference standards. It permits the size determination also of small molecules, even when scattering dissimmetry is not observable. Unfractionated heparins, eight fractions of a size fractionated heparin, and dermatan sulfates were analyzed by HP-SEC/TDA. The M values found for the heparin fractions were used to build up a calibration curve of a conventional HP-SEC system: the results obtained analyzing unfractionated heparin samples with both HP-SEC/TDA and HP-SEC were in excellent agreement, suggesting the possibility to use the TDA data to generate standard samples with known MD and intrinsic viscosity [eta]. Moreover, HP-SEC/TDA can successfully be employed also for the determination of the Mark-Houwink a and k parameters.