Instrumental neutron activation analysis (INAA) has been utilized for the analysis of 19 different fly ashes, 1 sample of coal and 3 samples of industrial emissions. Both short and long irradiations in a nuclear reactor have been used. The irradiated samples have been measured by means of a computer-based Ge(Li) gamma-ray spectrometer. The concentrations of 27 elements have been determined in the samples.