This study concerns the problems encountered in the molecular characterization of ultra-high molar mass (UHMM) hyaluronan samples. The determination of the molar mass distribution of UHMM polymers is fairly difficult. Shear degradation and non-newtonian Bow are the main difficulties in the fractionation on SEC columns. Considering these difficulties, the samples have remained previously characterized by off-line Light scattering and viscometry. The characterization by means of light scattering presents the problem of non linear angular variation of the scattering. We present a method to estimate reliable Values for molar mass and dimensions of UHMM hyaluronan polymers. To overcome the intrinsic viscosity shear rate dependence we have used a multi-bulb capillary viscometer. The persistence length of the UHMM hyaluronan polymer has been estimated.