Big sagebrush ( Artemisia tridentata) is a common shrub growing in the cold intermountain regions of western North America. The plant is an important food source for herbivores and was used in Native American traditional medicine. In this work, the essential oils were obtained from 3 individuals of A tridentata subsp. tridentata growing in southwestern Idaho. The essential oils were analyzed by gas chromatographic methods including chiral gas chromatography. The major components in the essential oils were yomogi alcohol (5.8%-30.8%), santolina epoxide (1.7%-10.5%), camphor (5.2%-20.1%), and ( Z)-tagetone (0.9%-8.9%). ( + )-α-Pinene, ( + )-β-pinene, ( + )-verbenone, ( − )-( E)-β-caryophyllene, and ( − )-δ-cadinene were the only enantiomers observed for these compounds. Camphene and camphor, on the other hand, showed wide variability in enantiomeric distribution. The enantiomeric distributions in A tridentata subsp. tridentata differ widely compared to other Artemisia species. There are large variations in the chemical compositions in A tridentata, both between subspecies and within subspecies.