The volatile components of the flowerheads of Centaurea calcitrapa L. (C.c.) and Centaurea sphaerocephala L. ssp. sphaerocephala (C.s.) were obtained by hydrodistillation and identified by GC and GC-MS. Altogether 96 components were identified, 66 in C. calcitrapa and 68 in C. spaerocephala, mostly fatty acids (32.8%, C.c. and 44.2%, C.s.) and hydrocarbons (32.3%, C.c. and 15.9%, C.s.). 9,12-Octadecadienoic acid (15.8%, C.c.) and hexadecanoic acid (30.7%, C.s.) were the most abundant fatty acids; tricosane (8.0%, C.c.) and heptacosane (4.9%, C.s.) were the main hydrocarbons. Sesquiterpenes were also present as hydrocarbons (10.1% for 14 components in C.c. and 9.2% for 13 components in C.s.) and as oxygen-containing sesquiterpenes (2.0% for four components in C.c. and 13.6% for nine components in C.s.). Copyright (c) 2005 John Wiley & Sons, Ltd.