The invention relates to a method of determining the motion vector of tissues in a biological medium. This method comprises the steps of: --acquiring a sequence of echographical images at a given repetition rate, --digitalising said echographical images and storing the so-digitalised images, --defining a digital pseudo echographical pulse, --effecting in a plurality of directions a convolution of said digital pseudo echographical pulse with said digitalised images and deducing therefrom at each point of said medium a plurality of pseudo echographical signals associated with said plurality of directions, --determining an estimate over said plurality of directions of the phase shift between two successive pseudo echographical signals and deducing therefrom the magnitude and the direction of said motion vector.