Wild growing, flowering Hyptis suaveolens (L.) Poit. (Lamiaceae) from 15 populations from El Salvador was collected and hydrodistilled. The resulting essential oils were analyzed by GC-MS. Principal component analysis of concentration data from 32 compounds showed differences of the chemical composition according to the geographic origin. In the southern area a fenchone-fenchol-chemotype was predominant, whereas in the northern regions the plants mostly accumulated 1,8-cineole. The essential oils of two collection sites from the southeast revealed high yields of alpha-terpinolene and sabinene. Some populations, however, showed unsteady compositions, indicating that intrapopulational chemical polymorphism occurs in Hyptis suaveolens. Copyright (c) 2004 John Wiley & Sons, Ltd.