The hydration of ol-pinene over catalytic PDMS membranes loaded with a USY zeolite is studied. The concentration profiles of reagent and products exhibited a pronounced initial induction period followed by a rapid increase of the reaction rate, suggesting an autocatalytic behaviour. The effects of the main reaction product, ol-terpineol, on the membrane transport properties are investigated. A simple diffusion-kinetic model which fits experimental concentration data quite well has been developed.