Abstract The influence of soil water stress on plant height, fresh and dry weight and essential oil content of Iranian Satureja hortensis L. was investigated. The volatile constituents of the aerial parts of cultivated S. hortensis were isolated by steam distillation and analysed by GCâMS. The results showed that greater soil water stress decreased plant height and total fresh and dry weight. The accumulation of oil increased significantly under severe water stress at the flowering stage, when the mean leaf water potential decreased from â0.5 to â1.6 MPa. This treatment affected the quantity of the essential oils more than moderate water stress during the vegetative and flowering stages. The main oil constituents are carvacrol and γâterpinene. The amount of carvacrol increased under moderate stress, while γâterpinene content decreased under moderate and severe water stress treatments. Copyright © 2002 John Wiley &amp; Sons, Ltd.