This study describes the application of the electrochemically generated molybdenum-based catalyst system MoCl5-e(-)-Al-CH2Cl2 to ring-opening metathesis polymerization of bicyclo[2.2.1]hept-2-ene (norbomene). The results are compared with those previously obtained by the WCl6-e(-)-Al-CH2Cl2 system. The polymer product has been characterized by H-1 and C-13 NMR, IR and gel-permeation chromatography techniques. This molybdenum-based catalyst system has led to a mainly trans stereoconfiguration (ca. 60%) of the double bonds, in contrast to the polymer obtained with the tungsten-based analogue, where the cis content is 60%. Analysis of the poly(1,3-cyclopentylenevinylene) microstructure by C-13 NMR spectroscopy revealed that the polymer having sigma(c) = 0.41 (fraction of double bonds with cis configuration) contains a slightly blocky distribution (r(t)r(c) > 1) of the double-bond dyads (r(t)r(c) = 1.44). In addition, the influence of reaction parameters, e.g. reaction time, electrolysis time and catalyst aging time, on conversion has been analysed in detail. Copyright (c) 2005 John Wiley & Sons, Ltd.