The transient deformation of red blood cells (RBCs) in a shear flow is studied by a three-dimensional numerical model proposed by the present authors.The RBCs are approximated by ghost cells consisting of Newtonian liquid drops enclosed by Skalak membranes.The RBCs have an initially biconcave discoid resting shape, and the intemal liquid is assumed to be the same to the fluid outside.The simulation is based on a hybrid method, in which the immersed boundary concept is introduced into the framework of the lattice Boltzmann method, and a finite element model is incorporated to obtain the forces acting on the nodes of the cell membrane which is discretized into flat triangular elements.