The antioxidant activities and the determined major components of six popular and commercially available herb essential oils, including lavender (Lavendular angustifolia), peppermint (Mentha piperita), rosemary (Rosmarius officinalis), lemon (Citrus limon), grapefruit (Citrus paradise), and frankincense (Boswellia carteri), were compared. The essential oils were analysed by GC-MS and their antioxidant activities were determined by testing free radical-scavenging capacity and lipid peroxidation in the linoleic acid system. The major components of the essential oils of lavender, peppermint, rosemary, lemon, grapefruit, and frankincense were linalyl acetate (28.2%), menthol (33.4%), 1,8-cineole (46.1%), limonene (64.5 and 94.2%), and p-menth-2-en-ol (34.5%), respectively. The highest DPPH radical-scavenging activity was obtained by the lavender essential oil and limonene, with RC50 values of 2.1 +/- 0.23% and 2.1 +/- 0.04%, respectively. Radical-scavenging activity against the ABTS radical was highest in peppermint essential oil (1.6 +/- 0.09). Lavender oil was most effective for inhibiting linoleic acid peroxidation after 10 days.