The mugwortArtemisia vulgaris L. (Compositae: Anthemideae) contains insect repellents which can be released from the plant tissues by combustion. Work was carried out to isolate and identify the repellent compounds. The dried, pulverized whole plants were steam-distilled to give a repellent essential oil which was fractionated by column chromatography. Active fractions were analyzed by capillary GC and by combined GC-MS. A number of compounds, mainly monoterpenoids, were identified. When tested as repellents against the yellow fever mosquitoAedes aegypti L. (Diptera: Culicidae), (±)-linalool, (±)-camphor, (+)-camphor, (−)-camphor, isoborneol, (−)-borneol, terpinen-4-ol, and isobornyl acetate were active at 0.14 mg/cm2 or higher. Nonanone-3, (α+β)-thujone, and bornyl acetate were active at 0.28 mg/cm2 or higher. β-Pinene, myrcene, α-terpinene, (+)− limonene, and cineole were active at 1.4 mg/cm2. Of the repellent compounds identified, terpinen-4-ol was the most active and was as effective as dimethyl phthalate.