The application of magnetic resonance spectroscopy (MRS) techniques to the study of neuropsychiatric disorders in childhood provides an extraordinary opportunity to advance the understanding of the neurobiological mechanisms underlying these disorders. All MR methods (MRS, magnetic resonance imaging (MRI) and functional MRI, (fMRI)) rely on the same basic principles. MRS offers several advantages over radionuclide neuroimaging techniques (positron emission tomography (PET) and single-photon emission computed tomography (SPECT)) for the study of children and adolescents, in particular its absence of ionizing radiation. The chapter considers evidence for abnormal concentrations of various metabolites detected with MRS in the brains of children with psychiatric disorders. MRS employs standard MRI devices to make measurements of chemical levels within the brain. MRS findings in children with acute or chronic neurologic insults are important because they may clarify the significance of biochemical changes identified in children with psychiatric diagnoses.