Abstract The hydrodistilled essential oil from aerial parts of Lychnophora pinaster Mart. was analyzed by GC and GC/MS. Plants were collected at 3-month intervals in a completely randomized design with six repetitions and the data was analyzed at the level of 5% of probability by Tukey's test. There was a significant difference for oil contents in the different seasons. The lowest oil content was obtained in the summer (about 50% inferior to the other seasons). Methyl (E)-cinnamate was obtained as the major compound (86â90%) of the 14 identified components. Key Word Index: Lychnophora pinaster Asteraceaeessential oil compositionseasonal variationmethyl (E)-cinnamate