The MRI Studies Group of CBDB consists of multidisciplinary specialists with expertise in neurology, psychiatry, psychology, physics, biology, and MRI techniques. This group pursues a variety of research agendas involving study of brain MRI scans per se and, also, collects, cata- logues, and archives MRI scans as a service to other research groups of CBDB. In particular, the PET and SPECT groups use the volume MRI scans for anatomically based analysis of PET and SPECT scans. More direct research interests of the MRI Studies Group include 1) morphometric investigations of brain structures putatively implicated in serious mental illnesses, such as schizophrenia, affective disorder, and Alzheim- er's disease; 2) gyral pattern assessments obtained by segmenting brain tissue away from surrounding skin and bone and generating surface render- ings of the cortex that rival postmortem views of the brain, and 3) functional brain images obtained by recently developed MRI perfusion scanning methods. A prominent characteristic of the MRI Studies Group has been the successful development of many innovative advances in methology which have substantially improved the accuracy, reliability, sensitivity, accessibility of morphometric MRI brain research. Among these accomplishments are improved methods for morphometry of cortical surface areas and sulcal lengths with the aid of surface renderings, refinements in semi-automatic segmenting techniques that produces corti- cal renderings of unsurpased fidelity, pioneering use of the two-dimen- sional cross-correlation function to quantitatively compare the degree of similarity of studies the CBDB database of monozygotic and dizygotic twin MRI's, and unique and valuable research resource for examining possible genetic correlates of schizophrenia and affective disorders by comparing MRI's within twin pairs that are discordant for illness.