An in situ H-1 nuclear magnetic resonance (NMR) technique has been employed to study the interaction of hydrogen with silica-supported ruthenium catalysts in the temperature range 300-473 K and at pressures of 10(-5)-760 Torr. In addition to an upfield NMR peak (called a) occurring at approximately -60 ppm and observed at low pressures (P < 100 Torr), we have noted the emergence of a second peak (called beta) occurring at approximately -30 ppm at elevated pressures (P > 100 Torr). These two hydrogen populations represent adsorbed hydrogen interacting with Ru metal particles, as indicated by the observed Knight shifts. The a hydrogen species exists in the form of less mobile hydrogen species al, or a mobile hydrogen species am with heats of adsorption determined by microcalorimetry to be about 70 kJ/mol and 40 kJ/mol, respectively. The heat of adsorption of the beta species was determined to be approximately 10 kJ/mol. Hydrogen adsorption isotherms were obtained from the NMR peak intensities calibrated by a gadolinium-doped lanthanum hydride internal reference. A higher dispersion of metal particles correlated with a larger amount of the weakly adsorbed beta hydrogen species. The H/Ru(surface) ratio was observed to be in excess of 5 at elevated pressures (> 500 Torr). The high H/Ru(surface) was due to the adsorption of large amounts of beta hydrogen.