Once they become symptomatic, cavernous malformations of the brain stem appear to cause progressive morbidity from repetitive hemorrhage, and can even be fatal. Twenty-four patients with long-tract and/or cranial nerve findings from their cavernous malformations of the brain stem were seen for initial evaluation or surgical consultation and thereafter received either surgical or continued conservative treatment. The decision to operate was based on the proximity of the cavernous malformation to the pial surface of the brain stem, the patient's neurological status, and the number of symptomatic episodes. Sixteen patients were treated by definitive surgery directed at excision of their malformation. In four patients, associated venous malformations influenced the surgical approach and their recognition avoided the risk of inappropriate excision of the venous malformation. Although some of the 16 patients had transient, immediate, postoperative worsening of their neurological deficits, the outcome of all except one was the same or improved. Only one patient developed recurrent symptoms: a new deficit 2 1/2 years after surgery required reoperation after regrowth of the cavernous malformation. She has been neurologically stable since the second surgery. One patient died 6 months postoperatively from a shunt infection and sepsis. The eight conservatively treated patients are followed with annual magnetic resonance imaging studies. One has a dramatic associated venous malformation. Seven patients have either minor intermittent or no symptoms, and the eighth died from a hemorrhage 1 year after his initial presentation. Based on these results, surgical extirpation of symptomatic cavernous malformations of the brain stem appears to be the treatment of choice when a patient is symptomatic, the lesion is located superficially, and an operative approach can spare eloquent tissue. When cavernous malformations of the brain stem are completely excised, cure appears permanent.