Zinc Selenide, in polycrystalline and single crystal form, and chemical vapor deposition (CVD) grown diamond films were studied with respect to their application as materials for electron-beam activated switches. The hold-off fields of the three materials were found to exceed that of semi-insulating gallium arsenide by at least an order of magnitude. Highest hold-off fields for pulsed voltage operation were recorded for diamond at 1.8 MV/cm. The electron-beam induced conductance in the 1 mm thick single crystal zinc selenide switches reached values of 0.5 (approximately ega cm2)-1 with an electron-beam current density of 20 mA/cm2 at electron-energies of 150 keV. This corresponds to an electron-beam induced reduction of switch resistance from 108 approximately ega to 2 approximately ega per square centimeter. The dominant carrierloss mechanism in the single crystal zinc selenide switch was found to be direct recombination of electron-hole pairs. In this material, the current, after electron-beam turn-off, decays hyperbolically with 90% to 10% falltimes in the range of hundreds of nanoseconds. The electron-beam induced conductivity in CVD grown diamond films of 1 micrometer thickness is due to the subnanosecond carrier lifetime less than three orders lower than that of single crystal zinc selenide. Both materials, single crystal zinc selenide and diamond, showed a lock-on effect in current. For diamond it could be demonstrated, as before for gallium arsenide, that this effect can be suppressed by proper choice of contacts.