A scanning Auger microprobe (SAM) equipped with a cylindrical mirror analyzer and noncoaxial ion gun has been adapted for ion scattering spectrometry (ISS). An optimally designed movable entrance aperture limits the scattering angle, providing high mass resolution and good sensitivity. Much of the electronics of the original SAM is employed for ISS, and switching the mode of operation is easily accomplished. The critical part of the apparatus is the entrance aperture, and its design is discussed in detail.