Superheated heated steam was used to extract volatiles from thyme leaves and black pepper fruits. Steam and extracted volatiles are collected in a condenser and essential oils are separated from the collected mixture by solvents and analysed by GC. Results show that the yield of extraction has an asymptotical evolution with time and increase with steam temperature and flow and it is higher for ground black pepper fruits. However, the quality of the extract is lower when the steam temperature is higher than 175 degrees C. (c) 2005 Elsevier Ltd. All rights reserved.