1. Magnetic resonance spectroscopy (MRS) is a powerful new neuropsychiatric research tool which allows for the noninvasive investigation of in vivo biochemistry. This review focuses on the recent applications of MRS to in vivo neuropsychiatric research. 2. The history of MRS as it has progressed from an bt vitro method of biochemical analysis to its current in vivo research uses is presented. 3. A brief overview of the physical priniciples of MRS, including methods for spectral localization, is discussed. 4. Applications of the different MRS modalities (H-1, P-31, F-19, Li-7, C-13 and Na-23) to various neuropsychiatric disorders such as Alzheimer's disease, schizophrenia, affective disorders, acquired immunodeficiency disease, etc, are reviewed. The study of both fluorinated neuroleptics and the antidepressant fluoxetine using F-19 MRS are discussed in greater detail. 5. Finally, potential future neuropsychiatric applications of MRS and specifically F-19 MRS are presented.