In this thesis, a phytochemical study of Allihemis tigreellsis has been undertaken and chemicalrninvestigation on the essential oil and solvent extract of the plant has been conducted. There arernno reports on the phytochemical study of the plant prior to this work.rnA. ligreellsis in the family Asteraceae, in the genuse Amhemis is the onl y species found inrnEthiopia. There are 20 species in the genus AlIlhemis di stributed in Southern Europe, South WestrnAsia, and North Africa. A. tigreensis has medicinal value and is important in tradit ional medicinernlike the other species in the genus.rnThe essential oil obtained by hydrodistillation was investigated by Ge, GC-MS, and NMRrnspectroscopy. Ten compounds constituting 66% of the oil were identifi ed, with bornyl acetate asrnthe major component. To the best of our knowledge, bornyl acetate (48%) is reported here fo rthernfirst time as a major component of the oil of Alllhemis species.rnThree sesquiterpene lactones At-8 (2E,6E)-8-(tetrah ydro-4-meth ylene-5-oxofuran-3-yl)-2,6-rndimethylocta-2,6-dienal, At-II Antheindurolide A, and At-7 dihydro-5-Â«2-(hydroxymethyl)-6-rnmethyl-3-methylene-7 -oxa-bicycio[ 4. I .OJhept-4-en- I -yl)meth yl)-3-methyl furan-2(3H)-one werernisolated and characteri zed from the solvent ex tract of the plant. 1 D and 2D-NMR, UV, IR andrnMS spectroscopic techniques were used for characterization of the compounds. To the best ourrnknowledge, the sesquiterpene lactone, At-8 is reported for the fi rst time. AI-1t was identifi ed asrnAntheindurol ide A, a sesqu iterpene lactone isolated previously from A. pseelldocotufa.