The essential oil of Senecio desfontainei Druce was analyzed by GC and GC - MS. A total of 41 compounds were identified. Oil profiles and contents of the flowers, leaves, stems and roots were determined. In the flowers, B-myrcene (38.1%), Cymene (19.7%), phellandrene (9.8%) and dehydrofukinone (10.1%) are the major constituents. In the leaves and stems dehydrofukinone is the major component constituting 42.8% and 77.6%, of the oil respectively. The major components of the root oil were, eremophilane (dehydrofukinone 46.9% and euparin 20.9%), caryophyllene 8.5% and farnesene (Z) B (3.7%). The antimicrobial activity of the oils was evaluated and showed broad and powerful activity aganist two Gram - positive, two Gram -negative and two fungi.