A spectrometer has been developed with the object of achieving a high diffraction efficiency, low background, and stability and convenience in operation. A mechanism is used to position the detector and crystal in relation to the sample, for determining extended spectra by Johann's and Cauchois' methods. Sample‐chambers with radiation shielding walls are used, and the outlet for fluorescent radiation is designed for reducing background. Microsamples can be used to simplify the evaluation of quantitative results. A vacuum‐chamber has been designed for further reducing background. 4×7 cm crystal lamellae on glass supports are prepared from blocks of NaCl or LiF and bent cylindrically for line focusing, or double‐curved for point‐focusing to increase the intensity at particular wavelengths, the focusing always being aberration‐free. The equipment has been calibrated for microquantitative determination of 30 elements, and an absolute sensitivity of 2×10−10g has been achieved for the elements Co&sngbnd;Zn.