The x‐ray transmission properties of a very thin polyimide window in the range 7–310 A˚ have been investigated. The window is nominally 0.24 &mgr;m thick and is supported by a hexagonal polyimide grid. Transmission of over 60% and 80% at the oxygenK&agr; and carbonK&agr; lines, respectively, have been achieved. The use of such windows as the entrance window of a gas scintillation counter (GSPC) operating as a broadband spectrometer at XUV wavelengths is discussed. Overall detector efficiencies of greater than 10% for wavelengths less than 150 A˚ are possible to achieve. ©1995 American Institute of Physics.