Abstract Dried aerial parts of 12 accessions of Iranian mints, three of which belonged to Mentha longifolia (L.) Huds. and the remaining of which belonged to Mentha spicata L., were used in this study. These were water distilled, and the essential oils analyzed by GC (FID) and GC/MS. Results indicated a significant variation in oil composition within the accessions. cis-Carveol (53.5â78.2%) was found as the main constituent in the oils of three M. longifolia accessions. The studied accessions of M. spicata indicated six different chemotypes, each of which was characterized by a high contribution of the following compound: 1 terpinen-4-yl acetate (51.7â55.3%); 2 carvone oxide (52.5%); 3 piperitone and menthol (49.3% and 15.7%, respectively); 4 carvacrol (49.6%); 5 isomenthone and piperitone oxide (39.1% and 23.3%, respectively); (6) p-cymene and trans-carvyl acetate (48.6% and 32.2%, respectively). The chemical variability of the tested accessions suggests the possibility of further exploiting and improving of the populations in a breeding program. Key Word Index: Mentha spicata Mentha longifolia Lamiaceaeessential oil composition cis-carveolterpinen-4-yl acetatecarvone oxidepiperitonementholcarvacrolisomenthonepiperitone oxidep-cymene trans-carvyl acetate