The effect of charges on sedimentation and diffusion of macroions is treated along the lines adopted by Svedberg‐Pedersen for the description of sedimentation, with the difference that the virtual electrophoretic motion of the macroions which gives rise to the charge effect is not equated to the real electrophoretic mobility. Furthermore the activity correction is introduced through the recently established representation, according to which a constant fraction of the counter‐ions may be considered to be permanently immobilized. Lastly, for the sake of simplicity, it is assumed that the frictional coefficient of the macroions does not depend on the ionic strength. On this basis a relatively simple description in terms of readily accessible parameters is obtained. The charge effects in sedimentation and diffusion are closely related, one to another, and to other polyelectrolyte properties. The physical significance of the results is discussed. The description is compared to experimental data in the literature and also to the second experimental part of this work: it is found that the main features of the charge effect are satisfactorily described under widely differing conditions, although some deviations indicate the limitations of the approximate treatment.