From the rhizomes of Atractylodes lancea, 2-[(2'E)-3',7'-dimethyl-2',6'-octadienyl]-4-methoxy-6-methylphenol (1) was isolated as a new natural product. The compound showed strong inhibitory effects on 5-lipoxygenase (5-LOX) and cyclooxygenase-1 (COX-1), but exhibited only weak antioxidative activities [IC50 = 0.1 microM (5-LOX), 2 microM (COX-1), 9 microM (PMN/FMLP), 28 microM (PMNIOZ)]. Moreover, five new acetylenes were isolated and elucidated as (3Z,5E,11E)-tridecatriene-7,9-diynyl-1-O-(E)-ferulate (2), erythro-(1,3Z,11E)-tridecatriene-7,9-diyne-5,6-diyl diacetate (3), (1Z)-atractylodin (4), (1Z)-atractylodinol (5), (1Z)-acetylatractylodinol (6) plus the known (4E,6E,12E)-tetradecatriene-8,10-diyne-1,3-diyl diacetate (7). Among the acetylenes, only 2 showed strong inhibition of 5-LOX and COX-1 activity (IC50 (5-LOX) = 3 microM, IC50 (COX-1) = 1 microM). In addition, the fatty acids linoleic acid, oleic acid and palmitic acid with previously established 5-LOX-/COX-1 inhibitory actions were identified as major constituents of the n-hexane extract and thus seem to contribute to the plant's in vitro activity.