The magnetic susceptibility of deoxygenated human red blood cell (RBC) is determined by Monte Carlo computer simulations using a primitive model comprised of a hard-spheres fluid with magnetic central point dipoles in presence of an external magnetic field. Two variations of this primitive model are considered. In the first case, a dipolar hard sphere describes a RBC, whereas in the second case it represents a reduced hemoglobin molecule. The magnetic susceptibility is obtained from the observed linear correlation between the magnetization and the external magnetic field. Very good agreement with experimental values is obtained for the second model. (c) 2006 Elsevier B.V. All rights reserved.