This study was undertaken to assess the antioxidant and antiproliferative potential of the essential oil of Hypericum hircinum L. subsp. majus (Aiton) N. Robson. Analysis of the oil composition revealed that sesquiterpene hydrocarbons (69.3%) dominate, cis-β-guaiene, δ-selinene and (E)-caryophyllene being the most representative. Significant values of antioxidant activity were found using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging assays. The essential oil revealed antiproliferative activity as evaluated on human glioblastoma (T98G), human prostatic adenocarcinoma (PC3), human squamous carcinoma (A431) and mouse melanoma (B16-F1) tumour cell lines by MTT assay.