Abstract: A single-pole-double-throw microwave monolithic switch is realized by employing shunt connected field effect transistors interconnected with microstrip transmission lines on a gallium arsenide substrate. A low-pass network, configured with quasi-lumped elements, is used to achieve a 90.degree. phase shift between the transistors and the input point. The FET gate width is selected to yield the appropriate source-drain capacitance, which forms one element of the low-pass network comprising the respective switch output path. Use of this inventive structure yields the bandwidth offered by the conventional shunt switch and the small size achievable in the series switch configuration.