The effects of selenium supplementation on apex and right ventricle myocardia of the rat heart were investigated using Fourier transform infrared (FTIR) spectroscopy by examining the changes in the frequency values of major absorptions arising from lipids and proteins. Cluster analysis was used to discriminate the selenium treated group from the control by utilizing two distinct spectral regions, belonging to absorptions arising from lipids and proteins, respectively. In addition, protein secondary structures were predicted using neural network analysis. The results suggest that selenium treatment at a non-toxic dose causes some significant structural alterations in lipids and proteins of rat heart apex and right ventricle myocardia, which might be revealing a slight deleterious effect of selenium supplementation. (C) 2008 Elsevier Ltd. All rights reserved.