Cell death induced by tumour-necrosis-factor-related apoptosis-inducing ligand (TRAIL) was believed to occur exclusively in tumour cells, suggesting that this drug is safe to use as an antitumour therapy. Concerns were raised, however, when cultured normal human hepatocytes were shown to be susceptible to TRAIL. Here we report that TRAIL induces apoptosis in the human brain. Our finding therefore argues against the use of TRAIL for therapy of human brain tumours. However, neuroinflammatory T cells that express TRAIL might induce apoptosis of brain tissue, indicating a potential target for treatment of multiple sclerosis.