Monolithic integration of pseudomorphic power and low-noise high electron mobility transistors (HEMTs) on a GaAs substrate has been demonstrated using specially designed multiple epitaxial layers. MBE-grown layers with three heterojunctions were selectively recessed to provide optimum structures for low-noise and power operations. At 18 GHz, a record power-added efficiency of 59% with 8dB gain and 0.4W/mm power density was obtained for the power HEMT. The low-noise device from the same slice achieved a noise figure of ldB with 9dB associated gain at the same frequency.