Technical Abstract: An investigation of the Indian folk remedy plant, Jatropha curcas, was performed to specifically identify the constituents responsible for the mosquito biting deterrent activity of the oil as a whole. Jatropha curcas seed oil is burned in oil lamps in India and part of Africa to repel biting insects, primarily mosquitoes. The seed oil was thoroughly analyzed by 1H NMR, 13C NMR, HPLC-RI, and GC-FID to identify the constituents in the oil. Identified constituents, both free fatty acids and triglycerides, were evaluated for activity in Aedes aegypti biting deterrent assays. Furthermore, an oil condensation trap was used to demonstrate that free fatty acids or triglycerides are partially volatilized during the combustion process. These compounds were found to be responsible for the biting deterrency of the burned oil. Specifically, oleic, palmitic, linoleic, and stearic acids were all active at 25 nmoles/cm2 above that of solvent control in Aedes aegypti biting deterrent assays. Oleic, palmitic, and linoleic acids were all more active than stearic acid in the same bioassay. Evaluation of the triglycerides containing each of these fatty acids revealed that tripalmitin, tristearin, trilinolein, and triolein all demonstrated significant activity above a solvent control at 10 ug/cm2, whereas tripalmitin was the most active. Due to literature reports suggesting insecticidal activity of the oil, J. curcas seed oil and its free fatty acid constituents were also evaluated against 1-day old Ae. aegypti larvae up to 500 ppm. Oleic acid was the only fatty acid having larvicidal activity against 1-day old Ae. aegypti larvae with an LC50 of 47.9 ppm.