Water-soluble ruthenium complex RuCl2(TPPTS)(3) have been used for the catalytic hydrogenation of unsaturated hydrocarbons, namely, 1-hexene, 1-heptene, styrene, cyclooctadiene, cyclooctene and benzene. Hydrogenation reactions were carried out under mild conditions. Optimum conditions for hydrogenation was evaluated and all substrate were studied at optimum conditions. The catalytic hydrogenation performances have been compared for aliphatic and aromatic hydrocarbons analogues. Results shows aliphatic hydrogenation occurs more easily compared to aromatic hydrogenation. Effect of addition of zinc chloride to aqueous solution on the hydrogenation of benzene showed that at some critical concentration of zinc chloride, partial hydrogenation of benzene to cyclohexene occurs. (C) 2003 Elsevier Science B.V All rights reserved.