Objective: This study was carried out to confirm prior evidence of an effect of a single nucleotide polymorphism (SNP) in the metabotropic glutamate receptor 3 (GRM3) gene (a putative risk factor for schizophrenia) on measures of N-acetylaspartate in healthy comparison subjects. Method: Fifty-four carefully screened healthy volunteers genotyped at SNP rs6465084 underwent magnetic resonance spectroscopic imaging (MRSI) at 3 T and selected neuropsychological testing. Results: The A/A genotype group exhibited a significant reduction of N-acetylaspartate/creatine levels in the right dorsolateral prefrontal cortex compared to the G carriers. A tendency in the same direction was seen in the left dorsolateral prefrontal cortex and in the white matter adjacent to the prefrontal cortex. Conclusions: These findings provide further evidence that GRM3 affects prefrontal function and that variation in GRM3, monitored by SNP rs6465084, affects GRM3 function.