The microstrip proportional counter (MSPC) is a new approach in gas-filled detector technology. In contrast with the classical multiwire proportional counter (MWPC) detectors, the electrodes of the MSPC are deposited by photolithographic techniques onto a rigid substrate. The technique offers many important advantages: An optimal energy resolution; The possibility of matching the electrode structure to the expected spatial resolution, i.e., smaller electrode distances than are possible for MWPCs; A much faster signal development than for the MWPC because of the small distance (few 100 µm) between the anode and cathode strips which allows the positive ion cloud created in the avalanche to be collected rapidly with reduced space charge effects and increased counting-rate capability; A rigid electrode structure which is not deformed under the action of an electric field; A relatively simple fabrication technique which allows the rapid replacement of damaged electrode structures. The applications of the MSPC within the fields of x-ray astronomy, neutron diffraction, high energy physics, and synchrotron radiation will be discussed. Review of Scientific Instruments is copyrighted by The American Institute of Physics.