Disturbances in glutamate function have been implicated in the pathophysiology of schizophrenia. We searched for mutations in the exons of the metabotropic glutamate receptor mGluR4 (GRM4) gene on human chromosome 6p21.3 and evaluated associations between these polymorphisms with schizophrenia in Japanese patients. Nine nuclear variants of 450G > T, 1455T > C, 2202A > G, 2389G > A (Val797 > Ile797), 2890A > G, 3601C > T, 3639C > T, IVS4-36G > A, and IVS5 + 29(CCGGG)1-2, were found. The Val797Ile variant, although found in both the patient and control groups, was rare and the only variant that causes a non-synonymous amino acid change. There was no statistically significant association between any mGluR4 gene polymorphism and schizophrenia. Thus, this study did not provide evidence for the contribution of the mGluR4 gene to schizophrenia in the Japanese.