Bipolar disorders (BD) have a strong genetic underpinning, yet no biological vulnerability markers for BD have been identified. Decreased volumes of subgenual cingulate (SGC) were replicated in familial bipolar patients. Presence of abnormality in unaffected subjects at genetic risk for an illness needs to be established before SGC volumes can be used as an endophenotype. This is the first study of SGC volumes in affected and unaffected subjects at familial risk for mood disorders.