To investigate the effects of bilateral posteroventral pallidotomy (PVP) for Parkinson's disease (PD), the authors reviewed the technique and neurological outcome in a number of patients who had undergone bilateral pallidotomy. The authors have previously reported the outcome of PVP in 25 bilateral and 25 unilateral surgeries, rating the patient's postural stability, speech, and total Unified Parkinson's Disease Rating Scale scores. A second, separate group of 23 patients who underwent contemporaneous bilateral PVP were evaluated for early onset idiopathic PD, levodopa failure syndrome, and severe bilateral dyskinesia as well as akinetic “off” states. Cognitive and psychological studies were reviewed in 10 patients who demonstrated preoperative impairments in spatial recognition and memory. Following surgery there were significant improvements in these cognitive deficits and no deficits were incurred by surgery. Published reports regarding bilateral operations for PD have emphasized the risks of speech and cognitive deficits. This study shows bilateral PVP to be effective, particularly in patients with bilateral symptoms, including disabling dyskinesia. Additionally, bilateral PVP does not cause additional cognitive or speech deficits. The techniques and indications as well as outcomes and complications are presented and discussed in this report in light of their controversial nature.