Methyltrioxorhenium (MTO) combined with hydrogen peroxide is a very useful catalyst for the epoxidation of ole-fins. In this work, we describe the efficient application of this system to perform epoxidation of several polydienes, such as polybutadiene (PB), polyisoprene (PI), randomic styrene-butadiene rubber (SBR) and low-molecular liquid hydroxylated polybutadiene (LHPB) showing that, depending on the amount of hydrogen peroxide added, it is possible to control the degree of epoxidation. This system shows to be sensitive to electronic and steric factors. The epoxidized polydienes were recovered in very good yields and characterized by H-1 and C-13 NMR and IR. (c) 2005 Elsevier B.V. All rights reserved.