Abstract Psorothamnus scoparius (broom dalea) was collected from the Jornada Experimental Range in south central New Mexico. Current year's growth was collected from 10 plants, all found within an approximate 50 in radius of the GPS coordinates N32°41.286â² and W106°46.922â² during June, 2000. Composite samples were steam distilled, and the essential oil was analyzed using GC with FID and GC/MS. Mass spectra and retention indices were used to identify 64 compounds. Retention indices and EI mass spectra are also provided for 15 unknowns. γ-Terpinene (22.3%), p-cymene (14.0%) and α-pinene (9.0%) were the major constituents of the oil.