<jats:title>Abstract</jats:title><jats:p>The fruit volatile oil of <jats:italic>E. camaldulensis</jats:italic> var. <jats:italic>brevirostris</jats:italic> was isolated by hydrodistillation and thereafter the fruit marc was extracted by ethanol. The volatile oil obtained was subjected to analysis using gas chromatography–mass spectrometry. Thirty‐eight volatile components were identified. The main volatile compounds in the fruit volatile oil were: aromadendrene (17.99%), α‐pinene (12.68%), <jats:italic>p</jats:italic>‐cymenene (5.39%), α‐gurjunene (6.65%), cubenol (9.23%), thymol (1.62%) and <jats:italic>p</jats:italic>‐cymen‐7‐ol (0.73%). The volatile components were classified into four groups: monoterpenes (20.6%), sesquiterpenes (33.8%), light‐oxygenated (8.1%) and heavily‐oxygenated (37.6%) compounds. The results showed that the concentration of sesquiterpenes and heavily‐oxygenated compounds were higher than the other two classes. The main compound in the ethanol extract of fruit of <jats:italic>E. camaldulensis</jats:italic> was isolated by semi‐preparative HPLC and identified as ellagic acid. The antioxidant activities of the fruits volatile oil and the ethanol extract as well as that of the tree bark were evaluated by the thiocyanate method. The ethanol extract of <jats:italic>Eucalyptus</jats:italic> fruit exhibited considerable activity compared with butylated hydroxyanisole (BHA) and tertiary butylated hydroquinone (TBHQ). The high inhibitory effect of the ethanol extract of fruit upon linoleic acid after 12 days might be related to the higher ellagic acid content. Copyright © 2002 John Wiley & Sons, Ltd.