New polymeric thermosetting resins prepared by the ring-opening metathesis polymerization (ROMP) of a commercially available vegetable oil derivative, Dilulin, and dicyclopentadiene (DCPD) have been prepared and characterized. A thorough characterization of the modified oil itself has been carried out to elucidate its structure. Grubbs' second-generation catalyst has been used to effect the ROMP of the strained unsaturated norborene-like rings in the commercial oil. Dynamic mechanical analysis of the resulting thermosetting resins has revealed that glass-transition temperatures ranging from 36 to -29 degrees C can be obtained when the proper ratio of oil to DCPD is employed. Thermogravimetric analysis has revealed that these resins have very similar temperatures of maximum degradation. Extraction analysis has indicated that all the samples had at least a 20%, soluble fraction and that the soluble fraction was composed of oligomers, unreacted triglyceride oil, or both. The effect of the soluble fraction as a plasticizer has also been explored. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 1788-1797, 2009