Abstract The essential oils of Conyza bonariensis, collected from five different places in the Amazon region were obtained by hydrodistillation and analyzed by GC/MS. The major components found in the oils from state of Mato Grosso were (E)-β-farnesene (19.1â23.3%), germacrene D (13.2â15.3%), β-caryophyllene (13.0â14.4%) and limonene (6.9â12.6%). The oils from the state of Para were rich in (E)- β-farnesene (20.1â30.9%), β-caryophyllene (13.3%) and limonene (3.7â22.9%). The oil from the state of Amapá was rich in limonene (58.4%).