Physical characteristics, chemical constituents and biological activities of the volatile oil of Ducrosia ismaelis Asch. have been studied. It is a light yellow volatile liquid with a strong aromatic odour and a specific gravity of 0.9573. IR, NMR and GLC spectrometry studies revealed the presence of free alcohols, alkenes and highly conjugated alkenes, aromatic functions, alicyclic structures and cyclic ketones. The pharmacological studies show a highly significant and dose dependent central nervous system depressant and marked neuromuscular blocking actions. Experiments on smooth muscles and heart show a parasympatholytic activity. It also exhibits significant antimicrobial activity against Staphylococcus aureus, Bacillus subtilis and Candida albicans. Further studies are being undertaken to find out its mechanism of pharmacological actions and to identify the active principle(s) responsible for those effects.