Water-distilled essential oils from dried aerial parts of Tanacetum argenteum (Lam.) Willd. subsp. argenteum (Lam.) and T. argenteum (Lam.) Willd. subsp. canum (C. Koch) Grierson were analyzed by gas chromatography and gas chromatography-mass spectrometry. In total, 27 and 32 components were identified representing 97.2 and 98.7% of essential oils of subsp. argenteum and canum, respectively. Main compounds of T. argenteum subsp. argenteum were alpha-pinene (67.9%) and beta-pinene (4.8%), whereas alpha-pinene (53.6%), 1, 8-cineole (14.8%), and camphor (4.7%) were the major constituents of subsp. canum. Essential oil of T. argenteum subsp. canum at 10 mu g/cm(2) with Biting Deterrent Index (BDI) value of 0.73 showed activity similar to N, N-Diethyl-meta-toluamide (DEET) at 25 mol/cm(2), whereas the activity of essential oil of subsp. argenteum was lower (BDI = 0.47) than subsp. canum and DEET. Based on 95% CIs, activity of beta-caryophyllene (BDI value = 0.54) and caryophyllene oxide (BDI = 0.66) were significantly lower than DEET. In larval bioassays, essential oil of T. argenteum subsp. argenteum showed LC50 value of 93.34 ppm, whereas T. argenteum subsp. canum killed only 40% of the larvae at the highest dose of 125 ppm. Among the pure compounds, beta-caryophyllene (LC50 = 26 ppm) was the most potent compound followed by caryophyllene oxide (LC50 = 29 ppm), which was also similar to (-)-beta-pinene (LC50 = 35.9 ppm) against 1-d-old Ae. aegypti larvae at 24-h post treatment. Compounds (-)-alpha-pinene and (+)-beta-pinene showed similar larvicidal activity. Activity of (+)-alpha-pinene with LC50 value of was similar to the essential oil of T. argenteum subsp. argenteum.