We carried out instrumental neutron activation analysis (INAA) as well as k0-based prompt gamma-ray analysis (k0-PGA) to measure the amount of the elements in onions and studied whether the onions collected from different sites can be
categorized based on the elemental concentration profile. Six elements (Na, Mg, Cl, K, Ca, Mn) and 3 elements (B, S, Cl) were
measured by INAA and PGA in the onions grown in two districts, Hokkaido and Saga, in Japan, respectively. After principal
component analysis, it was found that Cl was an important element to feature the producing districts of onions.