This study was prepared with the objective of directing the attention of the medical community to advances during the last decade in the operative treatment of cerebral ischemia, intracranial aneurysms, and cerebral and spinal vascular malformations. The requirements for specialized personnel, facilities, and instrumentation are detailed for those who are unfamiliar with the complexities of microneurosurgery. The importance of adequate training in the intricacies of extracranial-intracranial anastomotic procedures is stressed. Reported results of this operation are discussed. It is anticipated that a recently organized cooperative study will provide the data necessary for evaluation of long term benefits. Attention is given to grading the clinical status of patients with intracranial aneurysms in advance of surgery and the importance of operating upon good risk patients. How to manage the relatively large numbers of poor risk patients with aneurysms unsuitable for immediate operation is discussed. Sophisticated radiological procedures utilized in the diagnosis, management, and evaluation of therapy are described. The role and significance of properly administered anesthesia are discussed in relation to the performance of complicated and time-consuming microsurgery on the brain and spinal cord. The study group has tried to present this material objectively and to urge those individuals working in this difficult field to acquire the special skills and instrumentation of microneurosurgery, to implement the "team-of-experts" concept in the operating room, and to enlist the support of related disciplines.