The essential oils from the aerial parts ofGrindelia robustaandG. squarrosawere analyzed qualitatively and quantitatively by GC and GS/MS. Forty-nine compounds were identified by MS and RT data, 11 compounds were identified by comparison of their MS or RT with data from the literature. 1,2,3,4-Tetrahydro-1,1,5,6-tetramethyl naphthalene was isolated by means of preparative HPLC and its structure was characterized on the basis of MS and NMR evidence. The total quantities of the oils obtained by hydrodistillation was about 0.1% of the dry weight (flowers). Leaves and stems of theGrindeliaspecies differed in their oil content. (Iso)-bornyl C - and C -ester were found to be characteristic components of the essential oil ofG. squarrosa.