Two selected examples of PIXE microanalysis in ecophysiology are presented. Studies of heavy metal distributions in mycorrhizal and non-mycorrhizal roots of Plantago lanceolata showed different filtration mechanisms of Zn/Pb and Fe/Mn, both enabling plants to cope with metals present in the environment. Studies of the mechanism used by the beetle Chrysolina pardalina to eliminate excessive amounts of Ni revealed that Malpighian tubules are responsible for the elimination of this metal from the hemolymph. In both examples GeoPIXE software was used for true elemental mapping using the Dynamic Analysis method and analysis of spectra from selected micro-areas. Specimen thickness and matrix composition were obtained from proton backscattering spectra. Copyright © 2005 John Wiley & Sons, Ltd.