The effectiveness of essential oils obtained from lime (Citrus aurantifolia Swing.), kaffir lime (Citrus hystrix DC.) and betel vine (Piper betle Linn.) against bed bug (Cimex hemipterus Linn.) was evaluated by using contact method.Those plant essential oils at various concentrations of 0 (95% ethanol as control), 5, 10, 15, 20 and 25% were separately dropped on each filter paper (Whatman(R) No.1) for 0.5 ml (equal to 0, 0.4, 0.8, 1.2, 1.6 and 2.0 μl/cm2, respectively) and placed into petri dish with size of 90 mm in diameter.The treated filter papers were aired dry for 3 min.Then 10 bed bug adults were put into the petri dish.Mortality observations were made at 12 and 24 hrs after treatment.The experiment was CRD with 5 replications.Based up on 12 hrs LC50 values, the essential oil of betel vine was the most toxic to the bed bug with high activity of 1.31 tl/cm2, followed by essential oils of lime and kaffir lime, showed of 1.38 and 2.17 μl/cm2, respectively.As for 24 hrs LC50 values, the essential oil of betel vine still presented the most toxic effect to the bed bug with high activity of 0.80 μl/cm2, followed by of lime and kaffir lime, showed of 0.95 and 1.72 μl/cm2, respectively.The repellency test of the essential oils by using choice test was also investigated.The result presented that 0.8 μl/cm2 of all essential oils gave about 100%RI (Repellent Index) within 15 min when compared to control.