A collection of 19 accessions of Agastache foeniculum (anise hyssop), A . rugosa (catnip giant hyssop), A. nepetoides (Korean mint), and putative hybrids were analyzed for essential oil content and composition by gas chromatography (GC) and GC/mass spectroscopy. There was significant variation in oil content of the different lines of Agastache spp., ranging from 0.07 to 2.73 (percent volume/dry weight) for leaves and from 0.10 to 3.00 (percent volume/dry weight) for flowers. Variation in the essential oil composition was high among lines of A. foeniculum but low among lines of A. rugosa. Twenty-six compounds were identified in the essential oils, with methylchavicol being the major constituent (46.7-94.6% ) in 14 lines of A. foeniculum, A . rugosa, and putative hybrids. In contrast, 8-cadinol was the major oil constituent (39.6 % ) in A . nepetoides. Additional oil constituents found in these species in concentrations above 1% include P-bourbonene, bornyl acetate, y-cadinene, a-cadinol, 6-cadinene, a-camphene, P-caryo- phyllene, damascenone, P-ionone, isomenthone, a-limonene, linalool, methyleugenol, 0-myrcene, cis- ocimene, 7-octen-4-01, pulegone, and spathulenol.