Abstract: The invention concerns a method for identifying biological particles from a stack of holographic images obtained by means of an optical system. A stack of image blocks centred on the biological particle to be analysed is extracted from the stack of images and a reference block corresponding to the focus plan is determined. A characteristic magnitude is calculated for each block of the stack and the profile of this characteristic magnitude along the optical axis of the system is compared with a plurality of standard profiles relative to known types of particle. Alternatively, blocks of the stack are extracted from the stack of blocks for predetermined defocusing deviations and the extracted blocks are compared with standard blocks relative to known types of particle.