Viscosity of three polymers, namely polyisobutylene, cellulose acetate and polyschizophyllan, having different degree of flexibility is investigated over a wide range of concentrations and molecular weights. The data so obtained show a smooth variation in viscosity with respect to concentration of the polymers. The relationship betwe~n molecular weight of polymers and intrinsic viscosity or characteristic concentration, cch isobtained, by fitting the data to method of least squares. The cch values of the polymers were calculated using Graessley and Simha et al. models. Log n vs c/ c ch or c[n] were plotted to get the superpos it i on curves for every polymer. Where n is the reduced viscosity of the polymers. The data show that the deviations from these curves increase with the increase in rigidity of the polymer and it was not possible to scale the polyschizophyllan data using either of the above mentioned models. The data further show that the Graessley model is better than the others.