We investigated three polymorphisms in the NMDA receptor 2B subunit gene (GRIN2B) as a candidate gene for lithium response involved in glutamatergic neurotransmission. One hundred five bipolar patients treated with lithium for at least 5 years were analyzed. The lithium response was assessed as excellent - no affective episodes during lithium treatment; partial - 50% reduction in the episode index; or no response - less than 50% reduction, no change or worsening in the episode index. Genotypes for the -200G/T, 366C/G and rs890G/T GRIN2B polymorphisms were established using the PCR-RFLP method. Genotype distributions were in Hardy-Weinberg equilibrium for all three polymorphisms. No association was found between the three polymorphisms studied and the treatment response to lithium. The authors conclude that polymorphisms of the GRIN2B gene did not show an association with the treatment response to lithium in bipolar patients.