This study investigated the alterations in the electrical properties of human erythrocytes that occur during the insulin-induced internalization of insulin receptors (downregulation). Using a dielectric relaxation technique based on the Maxwell-Wagner effect, the data indicate a steady decrease over time in membrane conductivity, membrane permittivity, and conductivity of the cytosol in erythrocytes that have been stimulated to undergo downregulation by the addition of insulin. We hypothesize that variations in active transport properties as well as changes in membrane lipids and/or proteins occur during the process of insulin-induced downregulation of insulin receptors.