This paper presents an overview of the limbic brain and its distributed sub-systems. The extent of the limbic system has expanded in recent years. Among the brain areas that we now argue should be included in the extended limbic system are the medial prefrontal cortex, the insular cortex as well as the lower brainstem and spinal cord. In addition the limbic forebrain and limbic midbrain may be divided into medial and lateral divisions both anatomically and physiologically. This serves as an introduction to the papers that follow.