Both crystal despersion and diffraction grating instruments are routinely used for soft X‐ray dispersion in the fusion programme at the Culham Laboratory where the keV plasmas studied range from highly transient, high density ne≳1021cm−3, laser‐produced plasmas to relatively low density, ne≳ 1013cm tokamak plasmas. In this paper the soft X‐ray spetral features from these plasmas are discussed and the design parameters of appropriate instruments for X‐ray studies are considered.Useful spectral surveys of laser‐processed plasmas have been obtained using crystals bent convex in the de Broglie mode; higher aperture concave Johann configurations have been designed and constructed with multichannel read out for tokamak studies. Grazing incidence diffraction grating instruments have been operated in the photographic survey mode and as double channel monochromators. Operating experience with existing instruments is assessed. Examples of spectral information in the wavelength region ∼4 A˚ to ;∼400 A˚ are presented and their use in plasma diagnostic studies is discussed.