Sideritis phlomoides Boiss. & Bal., S. vulcanica Hub.-Mor,. S. vuralii Duman & Baser and S. caesarea Duman, Aytac & Baser are endemic species in Turkey. Water-distilled essential oils from the flowering spike of these plants were analysed by GCMS. beta -Pinens (35%). 1,8-cineole (15%) and alpha -pinene (15%) were the main component in the oil of S. vuralii. while beta -caryophyllene (8%) and caryophyllene oxide (7%) were the major constitutents in the oil of S.. caesarea. The oils from S. phlomoides and S. vulcanica tr were found to contain beta -caryophyllene (31% and 10%) as major constituents. alpha -Bisabolol (16%) was also found as a major component in the oil of Sideritis phlomoides. Copyright (C) 1999 John Wiley & Sons, Ltd.