Saturable radioligand binding of [(3)H]L-689,560 to the glycine site of the N-methyl-D-aspartate (NMDA) receptor was determined bilaterally in superior temporal cortex (BA22) and prefrontal cortex (BA10) taken post mortem from patients with schizophrenia and matched control subjects. A significant increase in NMDA receptor density above control values was found bilaterally in BA22 in schizophrenia, but not in BA10. The effect was greatest in those patients described as primarily type II, in whom the effect was significantly lateralized, with a greater elevation in the left hemisphere. A significant decrease in NMDA receptor density was found in rat frontal cortex following chronic antipsychotic drug administration, indicating that prior drug treatment was unlikely to have contributed to the differences in schizophrenia.