Water distilled essential oils from aerial parts of Thymus sipyleus subsp. sipyleus var. sipyleus, an endemic species of Turkey, collected from five different localities were examined by capillary GC and GC/MS. Seventy-seven compounds were characterized. Geranial (8.39–36.97%) and neral (3.08–25.56%) were major constituents of two of these lemon-scented oils. Linalool (21.77%) and α-terpineol + isoborneol (25.48%) were the main constituents in the oils of two collections, respectively. © 1995 Allured Publishing Corp.