Chemical composition of the essential oil of Bothriochloa pertusa (L) A. Camus, collected from temperate Himalaya, revealed the major categories of terpenoids as monoterpene hydrocarbons (26.45%), oxygenated monoterpenes (7.29%), sesquiterpene hydrocarbons (4.73%) and oxygenated sesquiterpenes (37.05%), in 82.31% of the total volatile constituents identified. Twenty-eight compounds were identified, the major of which are camphene (7.40%), limonene (14.90%), borneol (2.26%), Isobornyl acetate (2.01%), beta-caryophyllene (3.10%), intermedeol (24.72%) and acorenone-B (9.80%). B. pertusa contains higher percentage of monoterpene hydrocarbons and oxygenated monoterpenes in comparison to B. bladhi, the only other species of the genus analysed in detail. About 88% of the aromatic grasses are represented by tribe Andropogoneae, that spread globally by late Miocene, possibly a period of the greatest evolutionary diversity in aromatic grasses. (C) 1998 Elsevier Science Ltd. All rights reserved.