Polyisobutylene-supported second-generation Hoveyda-Grubbs catalyst is shown to be an effective nonpolar phase tag for ring-opening metathesis polymerization (ROMP). The catalytic activities of the supported Ru-carbene complex in ROMP are comparable to those of their homogeneous counter-parts. The separability of these catalysts leads to lower Ru contamination in the polymer products in comparison to the nonsupported Hoveyda-Grubbs catalyst. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 000: 000-000, 2012