Cymbopogon giganteus (Hochst.) Chiov., Cymbopogon nardus (L.) Rendle and Cymbopogon schoen anthus (L.) Sprend. Ssp. Proximus (Hochtst. Ex A. Rich.) Maire & Weiler plants are highly aromatic and reputed in traditional medicine in Benin. Physico-chemical studies and chemical composition of the essential oils (EO) extracted from the leaves of the three plants were realized by gas chromatography connected to a flame ionization detector (GC/FID) and by gas chromatography coupled to mass spectrometry(GC/MS). The major compounds (> 10%), marking the chemical profile of each of the essential oils studied, independently of the botanical variety considered, are constitued by the piperitone( 62.9%), geraniol (29.9-34.5%), citronellal (27.9-32.3%), limonene (10.8%-19.4%), cis-mentha-1(7),8-dien-2-ol (18.4%), trans-mentha-1(7),8-dien-2-ol (17.0-19.9%), carvotanacetone (17.9%), trans-p-mentha-2,8-dien-1-ol(12.0-17.4%), cisdihydrocarvone (10.1-17.2%), δ-2-carene (14.4%), myrtenol(11.9%)and citronellol(10.1-11.7%). The results of physico-chemical analyzes performed suggest a similarity between refractive index and density of the essential oil of Cymbopogon giganteus whose values are the highest. The values of the rotatory powers and acid index values did not remain homogeneous samples of essential oil of the same botanical species. They varied according to plant species studied and their origins.Key words: Cymbopogon, geraniol, piperitone, citronellal, cis-mentha-1(7),8-dien-2-ol, Benin.compounds of their essential oils focus in recent times, and effectively, the attention of researchers in the world of modern medicine. In Africa and in Benin in particular, the vegetation has a rich and
