The NMDAR2B subunit is the focus of increasing interest as a therapeutic target in a wide range of CNS pathologies, including acute and chronic pain, stroke and head trauma, drug-induced dyskinesias, and dementias. Due to significant pharmaceutical endeavor, an impressive collection of chemical leads has been developed which target the NR2B subunit, some of which appear to discriminate between closely related subtypes. We now have the benefit of a structural template for the ifenprodil binding site which should further improve future structure activity relationships. A growing appreciation of the likely extrasynaptic localisation of the NR2B receptor subtype and importance of NR2B protein modification, notably tyrosine phosphorylation, may explain its therapeutic importance. The apparent superior preclinical and clinical data for the second and third generation NR2B compounds is likely to reflect subtype selectivity, a unique mode of action and cellular location of the NR2B receptors in the CNS.