The work presented in this article concerns the development of a method for the determination of selenium-79 in fission product (FP) solutions resulting from nuclear fuel reprocessing. 79Se (T1/2
= 106 y) was measured using electrothermal vaporisation coupled with inductively coupled plasma mass spectrometry (ETV-ICP/MS) after a single chemical separation step to extract Se from the high activity solution (1010 Bq l−1). The results showed that the ion exchange method produced a solution sufficiently decontaminated with respect to major β/γ emitters and had a significant selenium recovery yield (85%). ETV parameters, for example furnace program, quantity of palladium nitrate used as chemical modifier, and gas flow rates, were optimised. The association of ETV and chemical separation eliminated all the interferences normally associated with the determination of 79Se. The concentration of 79Se measured in the fission products solution was 0.43 mg l−1.