This paper reviews the present status of GaAlAs/GaAs HBT technology and projects the impact of these devices on microwave and Millimeter-Wave integrated circuits. Devices with fmax above 120 GHz are described. Differential amplifiers are shown to have offset voltages with standard deviation below 2 mV and voltage gain as high as 200 per stage. Breakdown voltages (BVcm) above 20 V are demonstrated. Frequency dividers operating above 20 GHz are described.