Mercuric iodide detectors, operating at room temperature with the FET of the first stage of amplification cooled with a two‐stage Peltier element, have been used to detect low‐energy x rays from light elements excited by 2.0‐ and 6.1‐MeV &agr; particles. X‐ray lines from Na (1.04 keV) and Mg (1.25 keV) have been seen for the first time with room‐temperature energy‐dispersive detectors. A resolution of 390 eV at 1.25 keV was obtained. Further improvement of the resolution is believed to be achievable. However, even the present characteristics are adequate for many applications in x‐ray fluorescence and elemental analysis. Several such possible applications are suggested.