Excessive activation of glutamate receptors, most notably the N-methyl-D-aspartate (NMDA) subtype, appears to be a crucial factor in the sequence of cellular events which lead to irreversible ischaemic damage to neurones. The ability of newly developed antagonists of the NMDA receptor to reduce ischaemic brain damage has been assessed in cat and rodent models of focal cerebral ischemia. Non-competitive NMDA receptor antagonists such as dizocilpine (CAS 77086-21-6) which act at a site within the receptor operated ion channel markedly reduce (by more than 50%) ischaemic brain damage when administered prior to the ischaemic episode or 2 h after the onset of ischaemia. Competitive NMDA receptor antagonists, such as D-(E)-4-(3-phosphonoprop-2-enyl)piperazine-2-carboxylic acid, which act at the neurotransmitter recognition site are equally effective in reducing the ischaemic brain damage when administered prior to the onset of the ischaemic episode. The clinical utility of competitive and non-competitive NMDA receptor antagonists in man will, however, be determined not by their tremendous anti-ischaemic efficacy, but by their profile of adverse effects. Careful selection of the therapeutic target for NMDA antagonists will be necessary if beneficial effects are to be established in man.