Hydrogen adsorption on supported rhodium particles has been studied by H-1 NMR, volumetry, and microcalorimetry techniques, The amounts of hydrogen adsorbed on the metal and support have been evaluated. There is a good correlation between the shift of the NMR Line assigned to hydrogen adsorbed on the metal and the mean integral heat involved in this adsorption. This permits an estimation of differential shifts corresponding to each dose. From analysis of differential NMR shift and differential adsorption heat, it is deduced that the hydrogen-metal interaction becomes weaker and less energetic with adsorption. This effect is discussed on the basis of the heterogeneity of the adsorption sites and a modification of the electronic properties at the metal surface.