Evidence of glutamatergic dysfunction in schizophrenia associated with the N-methyl-D-aspartate receptor has historically demonstrated changes primarily attributable to neurons. We propose an astrocytic component to N-methyl-D-aspartate receptor dysfunction in this illness. We studied the expression of serine racemase, an astrocytic enzyme which synthesizes the N-methyl-D-aspartate receptor coagonist D-serine, using Western blot analysis in postmortem hippocampus and cortex in schizophrenia and a comparison group. We found increased expression in the hippocampus in schizophrenia. This is the first study to demonstrate alterations in schizophrenia of an astrocytic enzyme responsible for synthesizing a neuromodulator, and further evidence that astrocytes may play a direct role in N-methyl-D-aspartate receptor dysfunction in schizophrenia. © 2006 Lippincott Williams & Wilkins.