The ion mobilities of211At−and131I- in Na(Li)ClO4methanolic and ethanolic solutions containing N2H4· H2O were measured by horizontal zone electromigration. Basing on electrostatic model of Fuoss-Onsager the limiting mobilities, the tracer diffusion coefficients, the Stokes radii and the numbers of salvation were calculated for both ions and related to the other halides. These values of211At−and131I−are in good agreement with the other halide ions. This shows that the measurements method is able to be used for non-aqueous solutions with viscosities of η≦ g 1.5 cP and dielectric constants ofe≧;6.