Twelve patients who developed mania after a brain lesion are reported. Ages ranged from 20 to 83 years. Five patients had brain tumors (three frontal meningiomas, one temporal meningioma, and one temporal astrocytoma), four patients had stroke lesions (one frontal, one temporal, and two thalamocapsular), two patients had a traumatic frontal closed head injury, and one patient had a pituitary adenoma resection. Although seven patients had lesions restricted to the right hemisphere, four had bilateral or midline damage and one had a left hemisphere lesion. Damage to structures functionally connected to the obitofrontal cortex, mainly in the right hemisphere, seems to be associated with secondary mania. The possible roles of monoaminergic, genetic, and perinatal factors in the pathogenesis of secondary mania are discussed.