In the present paper the parametric decay instability of an extraordinary electromagnetic wave into an upper hybrid wave and a low-frequency electrostatic ion-Bernstein wave at different harmonics is considered. Expressions have been derived for homogeneous growth rates, thresholds, and convective thresholds at different harmonics of ion-Bernstein wave for this instability. Applications of this investigation to ionospheric modification experiment and polar cusp region of Earth's magnetosphere have also been pointed out. It has been found that the present decay instability is more important than the stimulated Brillouin scattering in homogeneous plasmas. ¿ American Geophysical Union 1993