The trans-β-farnesene synthase has been purified from basal and middle parts of growing needles of maritime pine (Pinus pinaster Ait.). This enzyme catalyses the conversion of farnesyl diphosphate to trans-β-farnesene, an acyclic sesquiterpene hydrocarbon. Its acidic property facilited its isolation by ionexchange chromatography. Its purification was continued on hydroxylapatite column and gel permeation and was greatly improved by dye binding chromatography. SDS-gel electrophoresis revealed a single band in the range of 45 kD for this enzyme which has been 1,030-fold purified. Trans-β-farnesene synthase requires for divalent cations with Mg2+ preferred to Mn2+ and for thiol reagents. Effects of inhibitors were examined and the enzyme activity was strongly affected by p-hydroxymercuribenzoic acid. The Km for farnesyl diphosphate was in the range of 5 μM and the optimum pH of activity was between 7-7.3.