This paper treats whistler amplification in the magnetosphere for conditions in which an energetic group of electrons interacts with the background plasma to produce wave growth. For the energetic group, the following forms of velocity distributions have been examined: pancake, anisotropic resonance, anisotropic Maxwellian, and an isotropic Maxwellian with loss‐cone. The work is distinguished from nearly all previous studies in that each case is subjected to rigorous stability analysis to determine whether the predicted instability should cause wave growth in time, or in space. This is very important in determining whether whistlers will be amplified when passing through an active region, or whether the region will simply be the site of continuous noise generation. The broad general conclusions of the work confirm that the presence of any anisotropy such that the particle energy transverse to the magnetic field is greater than that parallel to the magnetic field always causes instability in some sense. For the cases examined, the instability is generally amplified spatially until this ratio reaches some critical value, and temporally for further increases. The results are discussed in relation to observed whistler amplification and VLF emission