Advanced functional imaging techniques now make it possible to study in vivo the relationship between altered cerebral activation patterns and the psychopathologic and cognitive features of psychiatric disorders. Functional MR imaging (fMRI) offers new approaches to research questions in psychiatry that could not have been addressed earlier by positron emission tomography and single photon emission CT. Basic features of the biology of psychiatric disorders now can be elucidated by means of fMRI. Study designs involving fMRI capitalize on the technique's enhanced spatial and temporal resolution, noninvasive nature, and absence of radiation exposure.