Experimental data for a semicontinuous single-stage extraction process of terpenes from lemon essential oil using supercritical carbon-dioxide as a solvent ar e reported. Experimental runs were performed at a temperature of 316 K and pressures of 8.0 and 8.5 MPa. The experimental semicontinuous process was modelled assuming that the vapour phase leaving the apparatus was always in equilibrium with the liquid stationary phase inside the vessel, and the equilibrium conditions were represented by the Peng acid Robinson equation of state. In particular, the complex system 'natural lemon oil' was reduced to a mixture of some of the main components, limonene; gamma -terpinene; citral; linalool; and beta -caryophyllene. Since it is reached an excellent level of agreement between the calculated and the experimental extraction curves, the proposed thermodynamic approach seems to be reliable. Consequently, the thermodynamic characterisation of the system was extended to study a bit more complex process such as continuous countercurrent extraction. As an example a steady state simulation of a multistage column with the recycle of the solvent was reported. (C) 2001 Elsevier Science B.V. All rights reserved.