Platinum(0) and palladium(0) catalysts have been prepared by first exchanging the acidic protons in a variety of metal(IV) phosphates with platinum or palladium ions followed by their reduction to metal. The resulting supported catalysts were examined for their effectiveness in the hydrogenation of 1-octene, 1-, 3-, 4-methylcyclohexenes and cyclododecene. Rates of reduction and stereoselectivity were compared with a standard commercial palladium-on-charcoal catalyst and were found to vary widely by a factor of about 500, depending on the support used. Data are reported as relative rates of reduction. Steric effects due to substrate/support interaction played a major role in selectivity to hydrogenation. (C) 2002 Elsevier Science.B.V. All rights reserved.