Optical methods for investigation of erythrocyte dynamics and deformation are presented. In optical tweezers, tightly focused laser beam is used to trap and manipulate single microsized particles [1]. This allows observing deformation of single particles in various flow systems. In particular, this tool can be used for investigation of biological particles like red blood cells (RBC) behavior in different flow conditions. The second method is ektacytometry based on laser beam diffraction on dilute suspension of particles [2]. This method can determine the particle deformation by means of diffraction pattern change depending on the shear stress applied onto the particles or cells. The deformability of cells can be obtained implementing both methods using corresponding formulas. Here we present the two methods and the data that can be obtained using them. The objects under study are RBCs. These cells constitute the main part of blood mass and are responsible for oxygen supply to the tissues and removal of carbon dioxide. Their deformability is an important property determining the blood rheology.