The sedimentation velocity of hydroxypropyl cellulose acetate and cyanoethylhydroxypropyl cellulose molecules has been investigated in dilute solution in organic solvents. For these polymers, a linear dependence of the standard deviation of the displacement spectrum of macromolecules in an ultracentrifuge field on the sedimentation boundary shift was observed. The method of moments with linear approximations was used to exclude the concentration and diffusion effects and to determine the inhomogeneity parameter of the samples, M(z)/M(w). They range from 1.4 to 7. The inhomogeneity of fractions and the initial unfractionated samples is compared.