Laboratory bioassays were performed to test the repellent properties of 5 plant-extracted essential oils against the Argentine ant, Linepithema humile (Mayr). Three concentrations (0.10%, 1%, and 10% in n-hexane) of peppermint, spearmint, wintergreen, cinnamon and clove oils, as well as a negative control [n-hexane] and positive control [Cinnamite^™] were evaluated in choice tests to evaluate repellency against Argentine ant workers by counting the number of ants entering a preferred harborage that was treated and then aged for 2 h (fresh) or 7 d (one-wk-old). When deposits were fresh, all oils at all concentrations were repellent, with repellency defined as statistically fewer ants in harborages compared with harborages treated with only solvent (hexane). After the deposits were aged for 7 d, 4 of the 5 oils formulated at the 0.10% concentration were no longer repellent, whereas only spearmint had retained its repellent property. At 1% and 10% oil concentrations all 5 oils were repellent, whereas only 1% winter-green was slightly less repellent.