The hydrogenation of aromatics, i.e. benzene, toluene, alpha-methylstyrene, anisole, and ethyl benzoate, can be carried out under a very low (1/12000) catalyst to substrate ratio, and mild reaction conditions (80 degrees C, 6 atm of H2O), on Rh and Ni organometallic complexes anchored on USY zeolites. A strong cooperative effect between the faujasite surface and the transition metal surface complex is thought to be responsible for the simultaneous enhancement of concentrations of arene and H-2 in the neighborhood of the catalytic centers, and for the observed electronic effects.