ABSTRACT.1The elemental composition of 249 adult Brimstone butterflies (Gonepteryx rhamniL.) was studied by wavelength dispersive X‐ray fluorescence spectrometry, to determine whether site/population‐specific differences could be detected. The chemical elements studied were K, Ca, Fe, Cu, Zn, Ti, P, CI and S.2Marked differences were found in the chemical composition of the two sexes, and between individuals caught on different sites and in different years and seasons.3Multivariate analyses of the data using principal component analysis and canonical variate analysis showed a clear separation of the butterflies by sex, and within each sex, by seasons. Of the elements studied, the main discriminating ones for this butterfly were K, Ca, P, Zn, CI and S.4Whilst differences in chemical composition appear to result from variations in the composition of soil and food‐plants in different localities, any site/population‐specific differences are soon masked by the passage of time, as adults age and feed. This makes the technique of limited value in the study of dispersal in this