The operating characteristics of an unstable resonator Q-switched Nd-YAG laser are reported and its suitability for a number of applications has been tested. At repetition rates up to 50 Hz, output energies of 150–200 mJ are obtained with a beam divergence of 0.25 mrad half-angle. Single longitudinal mode operation has been achieved either with passive Q-switching or with an active slow Q-switch.