The microinstability theory of the two-energy-component toroidal system is developed and applied to systems typical of those in proposed fusion break-even experiments. The energetic ion beam distributions Fb(v||, v⊥, t) obtained from approximate solutions of the Fokker-Planck equation are studied for high-frequency microinstabilities arising from or in both transient and collisional equilibrium states. For typical beam-plasma parameters, the system is shown to be stable to high-frequency modes during the parallel injection of a continuous, monoenergetic source.