In two preceding papers (Wu and Lee, 1979, Lee, et al., 1980) an effective loss-cone distribution function is used in the stability analysis relevant to the theory of auroral kilometric radiation. Furthermore, in these discussions it is assumed that the popultion of low-energy background electrons prevails over that of the energetic electrons. Obviously, this assumption may not be justifiable at high altitudes. The present work considers a loss-cone distribution close to that observed and, moreover, includes the effect of a parallel electric field on the loss-cone distribution function. It is found that this effect tends to enhance the growth rate. We have also removed the assumption concerning the high population of background electrons. We find that at high altitudes, where the density of energetic electrons may dominate and the usual cold electron dispersion relation is invalid, the cutoff frequency of the X mode can be significantly affected by the energetic electrons and thereby the growth rate is indirectly altered. In the present discussion, the emission of the auroral kilometric radiation is studied over a range of altitudes. We have considered three density models and two electric field models. In addition to the temporal growth rates, the corresponding e folding distances of spatial amplification are also computed and discussed.