Crude hydromethanolic (80% methanol) extracts produced by maceration of Onopordum acanthium leaves and Spartium junceum flowers were tested for cytotoxic effects against glioblastoma U-373 tumour cells. Onopordum acanthium extract was found to be ~5 times more cytotoxic than Spartium junceum (IC50 values of 309 and 1602μg/ml, respectively). Similar to most chemotherapeutic agents killing through the intrinsic pathway, Onopordum killed the cells via apoptosis, which was confirmed by the activation of caspase-3. Spartium exerted its weak cytotoxic effect, presumably by a caspase-independent, non-apoptotic form of necrotic-like programmed cell death. Onopordum acanthium is considered a promising plant for the researchers investigating putative biological activities, particularly antitumour and immune-related activity.