Silica-supported heteropoly acid H3PW12O40 (PW) has been found to be a very efficient and environmentally benign solid acid catalyst for the liquid-phase isomerisation of alpha-pinene oxide (1). The reaction has been performed in cyclohexane solutions at 15-40 degrees C to give campholenic aldehyde (2) and trans-carveol (3) as the main products in up to 98%, total yield, with 70% selectivity to more valuable product 2. Both 2 and 3 are expensive ingredients in the fragrance industry. No PW leaching has been observed during the reaction. The catalyst is easily separable from the reaction mixture and reusable without loss of its activity and selectivity. (c) 2005 Elsevier B.V. All rights reserved.