[en] The method for neutron activation analysis is a well-known technique for trace amount elemental analysis. At GKSS mainly the special technique of instrumental neutron activation is used as an absolute method. For this purpose gamma radiation measuring systems with high resolution are necessary, with the main components such as germanium detector, amplifier and multichannel-analyser. These systems have to be calibrated on an absolute scale by gamma radiation standards. The precise calibration of these devices is repeated every year, the detection probability is checked for each series of mesurements in time intervals of about one weak, and the energy is calibrated for each individual measurement. (orig./RW)