Abstract: The volatile oil of Cymbopogon proximus was prepared by hydrodistillation method and analyzed chemically by GC/MS. The chromatogram showed 8 peaks corresponding to eight components with piperitone representing 72.44% of the oil`s composition. Oral and intraperitoneal (i.p.) administration of the volatile oil to male, female rats and mice resulted in LD50 values in the range of 1.9- 2.6 mL kg-1 with an oral absorption of 80-90%. I.p. administration of the oil to anaesthetized rats (0.2-1.6 mL kg-1) decreased the arterial blood pressure in a dose-dependent manner without significant changes in the heart rate except in the largest dose tested where a 16% decrease was observed. The induced decreases were not antagonized by atropine or mepyramine but were significantly reduced by indomethacin. The oil did not induce significant changes in the ECG. I.p. administration of the oil (1.2 mL kg-1) to mice before induction of convulsions with electric shock, pentylenetetrazole, picrotoxin and strychnine resulted in complete protection only against the electrically induced convulsions. I.p. administration of the oil to pigeons in doses of 0.4 and 0.8 mL kg-1 significantly protected against ouabain-induced vomiting. The results of these studies pointed to the involvement of prostaglandins in the oil-induced cardiovascular depressant effects and a probable antidopaminergic and antiglutamic-aspartic acids in the antiemetic and anticonvulsant effects, respectively.