The essential oil of aerial parts of Porophyllum ruderale (Jacq.) Case. was analysed by HRGC, HRGC-MS (quadrupole) and 26 components (93% of the total composition) were identified. The enantiomeric distribution of beta -pinene, sabinene. 4-terpineol and alpha -terpineol was studied by multidimensional HRGC-HRGC. The major component was sabinene (64%) with an enantiomeric purity of 97% For (+)-sabinene. Copyright (C) 1999 John Wiley & Sons, Ltd.