Using the unsmoothed ILS coordinates of the instantaneous pole (Yumi and Yokoyama, 1980) the stability of the amplitudes and phases of the main harmonic terms in the polar motion are investigated. It has been established that the amplitudes and the phases were not subject to systematic fluctuations. As for the amplitude A and the phase P of the Chandler nutation, it seems that the amplitude forms a periodic function of time enclosing as the most promment the components with 53.0 and 34.5 year periods, while the phases kept stable over longer time intervals, apart from jump-like change from 1925 to 1940.