A technique is suggested for creating anisotropic and emissive carrier distributions in semiconductors or other crystals at low temperatures. As an example, application of the technique in the re‐entrant (negative‐mass) regions of heavy holes in germanium and silicon, in conjunction with cyclotron resonance using circularly polarized microwaves, is discussed. These distributions are expected to be short‐lived (of order 0.2 to 5 m&mgr;sec), but more anisotropic than those obtained so far in these regions by applying steady‐state optical excitation alone. The nonequilibrium distributions would be created by excitations (pulsing, for example) with risetime shorter than the carrier‐phonon scattering time. Recently, the increasing purity of materials and speed of electronic instruments have approached the theoretical requirements of this method.