Magnetic resonance imaging (MRI) can be usedto quantify brain morphology, tissue microstructure, and function. These measurements can be used to identify the tissue changes that accompany brain injury and disease. For example, high spatial resolution structural images can be ana-lyzed to map local reductions in cortical volume. Diffusion weighted imaging can be used to reconstruct axonal fiber pathways in brain white matter and to assess fiber integrity. Functional imaging provides maps of neuronal activity during rest and task performance, and hence can identify the cortical networks that underlie sensation, memory, emotion, and cogni-tion. These imaging techniques have been applied to a wide range of neurological and psychiatric diseases to shed light on the role different brain regions play in the pathophysiology of each disease. This talk will focus on the specific examples of schizophrenia and Alzheimer's disease. Key imaging studies will be described that implicate specific brain regions in the development of disease symptoms. Prospects for identifying imaging endophenotypes of these diseases will be discussed. Finally, imaging biomarkers will be described that may be useful for monitoring disease progression and treatment.