This study describes the qualitative analysis of the polymerization reaction of DCPD (DiCycloPentaDiene) and its reaction products. The polymerization was carried out using WCl6/Si(allyl)(4) (1), first generation Grubbs' (2) and second generation Grubbs' (3) catalysts. When system 1 was used as a catalyst, solution concentration determined whether soluble or insoluble polymer was obtained. When Grubbs' catalysts were employed, insoluble polymer was formed in all cases. The ring opening metathesis polymerization (ROMP)-reaction and the resulting polymers were monitored in situ via FT-Raman-spectroscopy. Using FT-Raman-spectroscopy, the stereospecific nature of the forming polymer can be determined during the polymerization reaction. The obtained spectra illustrate that the linear polymer has a prevailing cis double bond configuration, while the polymer formed using the 1(e) generation Grubbs catalyst has a predominant trans double bond configuration. The second generation Grubbs catalyst exhibits a poor stereoselectivity. These results are in accordance to literature data where the stereospecific nature of these polymers where determined using NMR-spectroscopy. (c) 2006 Elsevier B.V. All rights reserved.