Semiconducting X-ray detectors with low noise and high resolution have recently become available for the less than 20 keV range which is the region of interest encountered in the examination of X-rays produced in the electron microprobe analyzer. Although their energy resolution is generally less than that of crystal spectrometers, they offer special advantages including simultaneous collection of all detectable X-ray signals, high collection efficiencies, wavelength measurement independent of specimen position, and rapid collection of data in a form compatible with computer processing. Added to an electron microprobe, they provide a method of detecting in several minutes all elements with atomic number greater than sodium and present in quantities as small as a few tenths of a percent. Quantitative analyses are possible provided care is exercised in evaluating background spectra and peak overlap.