Using citrated blood of eleven healthy donors the density distribution of red blood cells (D.D.C.) was determined and eight fractions from each sample separated. Separated red cells were resuspended in their own plasma and employed for the electric mobility measurements. The Ruhenstroth-Bauer Cytopherometer was used at a current of 5 ma. at 24 C. The range of migration of red cells was found to be 0.855 to 1.47 x 10-4cm.2v-1sec.-1. In separated fractions the older the cells the slower they migrated in the electric field.