We review work on heterojunction FETs (HFETs) fabricated from III–V compounds, with emphasis on the unique properties of such devices and their applicability to high-speed logic circuits. After discussing their general properties, including their uniquely high carrier mobility and fast switching speed, we discuss HFETs investigated at the IBM Thomas J. Watson Research Center, i.e., the semiconductor-insulator-semiconductor FET (SISFET) and quantum-well metal-insulator-semiconductor FET (QW-MISFET)—and their possible circuit applications. Finally, the opportunities for achieving a circuit performance level beyond that offered by the GaAs-(Al,Ga)As materials system are explored.