Renewable resources have been utilized to control the degree of crosslinking during ring-opening metathesis polymerizations (ROMP). In this regard, the addition of monoterpenes to thermosets created a sustainable method for adjusting the physical properties and thermal stability. A number of monoterpenes with alkenes were examined as monofunctional reactants. The presence of these monoterpenes, such as beta-pinene, during the ROMP of dicyclopentadiene altered the degree of crosslinking and plasticized the thermoset. The resulting physical properties were tailored to obtain desired modulus and glass transition (T-g) temperatures. The influence of time, temperature, weight percent beta-pinene, and different metathesis catalysts was examined by dynamic mechanical analysis, thermogravimetric analysis, and FTIR spectroscopy. A comparison of beta-pinene with other monoterpenes, such as carvone, limonene oxide, myrcene, and d-limonene, resulted in a reactivity profile for this general method. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 3719-3727,2011