Following the repair of a ruptured anterior communicating artery aneurysm, a patient had a severe anterograde amnesia with sparing of other intellectual functions, apathy and loss of volition, altered arousal, and partial diabetes insipidus. Postmortem examination of the brain revealed bilateral destruction of the septal gray, nucleus accumbens, and nucleus of the diagonal band of Broca. Also involved in the lesion were inferior portions of the anterior limb of the internal capsule and globus pallidus. Discrete, microinfarcts were present in the paraventricular hypothalamic gray. Long-term therapy with desaminoarginine vasopressin nasal spray had no effect on the patient's neuropsychologic deficits.