The hydrogenation of a copolymer of styrene and butadiene (SBR) catalyzed by Ru(CH=CHPh)Cl(CO)(PCy3)(2) was experimentally investigated within the temperature range of 120-160degreesC at P-H 2 of 300-1200 psi, and a catalyst concentration of 10-78x10(-6) M. Special attention was paid to minimizing the catalyst metal residue and crosslinking in the product. The results indicated that high-quality hydrogenated SBR was achieved without crosslinking and the metal residue was less than 7 ppm without a post-treatment.