A method is provided for assisting the piloting of a rotorcraft in which vertical speed variation (DVZ) of the rotorcraft is determined as a function of a horizontal speed variation (DVH) of the aircraft and as a function of data representative of the power (W) absorbed for providing the rotorcraft with lift and forward advance, the ratio between variation speed vertical (DVZ) and the horizontal speed (VH) of the rotorcraft is calculated, and a piloting assistance symbol is presented on a display in a position (.alpha.) that is a function of the ratio.