The anatomy and physiology of the structures in the region of the third ventricle are reviewed as they pertain to the various surgical approaches to this area. The peri-third ventricular area of the brain, an area less than 1% of the whole brain, is the center for a host of homeostatic mechanisms; temperature, osmolality, pituitary endocrine function, sympathetic and parasympathetic control, appetite and for a variety of behavioral drives, e.g. sex. In addition, memory circuits pass through this area, although current models exclude the immediate hypothalamus as playing a major role in memory. The various surgical approaches are reviewed and unavoidable injury as a result of the lesion or complications related to the surgery are considered in three categories: those that result from the surgical exposure itself; those that result due to maintaining the surgical exposure, e.g. retractor damage; and those that are unavoidable as a result of the infiltrative nature of the lesion itself. The causes of injury are further categorized into those due to arterial, venous, or direct cerebral tissue injury. Ways to minimize complications are presented.