Parametric decay of an electron Bernstein pump wave into an electron Bernstein sideband wave and a nearly perpendicularly propagating ion acoustic (or electrostatic ion cyclotron) decay wave is studied. When incorporated with appropriate nonlinear scattering processes, this instability process along with its cascading is proposed to be the generation mechanism for the downshifted peak (DP) and 2DP features as well as the upshifted peak (UP) feature in the stimulated electromagnetic emission spectrum observed in ionospheric heating experiments. It is found that the instability can be excited most favorably when the heater wave frequency f0 is in a very narrow frequency range near the third harmonic of the electron cyclotron frequency fc of the ambient ionosphere. Moreover, the frequencies associated with the low-frequency decay mode decrease as f0 is increased toward 3fc, consistent with experimental observations. ¿ American Geophysical Union 1995