The polymerisation of exo,endo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid esters initiated by (H(2)IMes)(PCy3)(Cl)(2)Ru=CHPh was used as a model reaction to investigate the influence of various donor solvents on the polymerisation reaction and the polymer properties, by using a fast and simple screening method. The results revealed that especially molecular weights and molecular weight distributions are strongly affected by the functional groups present in the reaction mixture. Thus, polymer properties can be effectively adjusted by addition of donor solvents to the reaction mixture. The method can also be used to estimate the influence of various functional groups on the course of the polymerisation reaction of functionalised monomers. (C) 2003 Elsevier B.V. All rights reserved.