Polymerisation of alpha-pinene using vanadium oxide (5 wt.% metal) supported on activated carbon was carried out at room temperature and 90degreesC. Polymers of low molecular weight were obtained after 100h of reaction and 30% conversion was attained. The presence or absence of light has an important role in the reaction, suggesting that alpha-pinene polymerisation takes place via a radical mechanism. The role of the catalyst seems to be to increase the formation of radical initiator species such as peroxides. For the bulk catalyst (1.25 g) 50% conversion was obtained after 2 h at 90 degreesC, and only isomerisation products of alpha-pinene, such as camphene and tricyclene. In situ XRD was carried out using the same experimental conditions of catalyst pre-treatment, and the phases identified for the supported and bulk catalyst was a mixture of V2O5/N6O13 and V2O5. The nature of vanadium species seems to be related to the catalyst behaviour.