The catalytic cyclisation of citronellal was studied over Zr-zeolite beta, micro/mesoporous Al-MSU-S-FAU, and microporous HY catalysts. All samples showed good activity in the cyclisation of citronellal to form isopulegols with >97% selectivity. A high diastercoselectivity for (+/-)-isopulegol of similar to93% was observed over Zr-zeolite beta, whereas Al-MSU-S-FAU and HY showed a lower selectivity of similar to65%. Zr-zeotite beta was synthesised in a range of Si/Zr of 75-200 with the use of fluoride and zeolite beta seeds. Zeolite beta with Al and Ti substitution was less active and selective than Zr-zeolite beta. The rate of reaction strongly depended on the type of solvent used, but the reaction could also be carried out without any solvent. A hydroxylated surface is important for good activity. This is consistent with the proposed mechanism, where both Lewis and Bronsted acid sites are essential for the reaction. (C) 2004 Elsevier Inc. All rights reserved.