The composition of the essential oils of four species of Sideritis, th
ree of them endemic to Turkey, was investigated by GC and GC-mass spec
trometry. They were characterized by the presence of a high percentage
of monoterpene hydrocarbons. alpha- and beta-pinene were the main con
stituents of S. congesta and S. argyrea, while limonene was the major
one of the oil of S. perfoliata. S. condensata provided an essential o
il with high proportions of beta-caryophyllene and alpha-pinene.