In the study of the interaction of RF and MW fields with biological systems particular attention has been recently devoted to microdosimetric research. In this paper a microdosimetric study on erythrocytes is proposed. Facing this topic, two fundamental steps are needed: the set up of a proper membrane dielectric model valid up to the RF and MW range, and the set up of an appropriate EM solution on the cell environment. Concerning the first point, an accurate estimation of the membrane dielectric model and of its uncertainty has been performed, from permittivity measurements of erythrocytes solutions. Focusing on the second point, a quasi-static EM analysis solving the Laplace equation has been chosen. An analytical approach has been applied on simplified spherical cell geometry, while a numerical solver has been used for erythrocyte shaped cell. In this context the fundamental role of the dielectric membrane modeling on results reliability has been highlighted. © 2009 IEEE.