The nonideality of the epithermal neutron flux distribution at a reactor site can be described by a 1/E1+ spectrum representation, with parameter being a measure of the nonideality. -values were determined in 3 typical irradiation positions of the TRIGA MARK II reactor of the Jozef Stefan Institute, Ljubljana, Yugoslavia, using the Cd-ratio for multi-monitor method. The simpler Cd-ratio for dual monitor method (monitors:197Au–94Zr) also yielded reliable results. This characterisation is of use in the k0-method of NAA, which is recently introduced at the Institute.