The sedimentation constant of hard spheres decreases with concentration, due to the effect of backflow and distortion of the hydrodynamic field. For macromolecules at the 0-temperature, this effect of concentration is much smaller than that of equivalent spheres. Pyun and Fixman suggest that intertwinement of macromolecules gives rise to increase of the sedimentation velocity. However, their detailed model of intertwined molecules is unrealistic. An alternative model is proposed by considering a pair of intertwined homologous molecules with N~ and Nj segments respectively, as a single molecule with (N~+ Nj) segments. This model leads to a simple expression for the concentration coefficient in the sedimentation velocity, containing an adaptable parameter, x~j, characterising the probability of intertwining. The probability of intertwining is put equal to the probability of intermolecular approach to within a distance of Rint and xij is defined by xij = 2Rint/(R i 4-Rj), with R i and Rj the friction equivalent molecular radii. From experiments on a number of sharp polystyrene fractions in cyclohexane at T = 0, a value x,i = 2.2 is deduced, decreasing with increase of molecular weight. Qualitative agreement is found between experimental results and predictions from the model. Quantitative agreement is not expected in view of uncertainties in the model. In ternary systems, containing molecules of different velocity, probably additional effects operate besides backflow, field distortion and intertwinement.