The cooperative aneurysm study was begun in 1957 and remains vitally active today. The project is the first in-depth study supported by the National Institutes of Health of a major human disorder. Because no single center could accumulate sufficient cases for meaningful analysis, the participation of many US and foreign centers was obtained. Dr Sahs, the prime engineer from the beginning, and his colleagues update in this volume the recent results of the project, supplementing the 1969 publication of initial results.
The authors systematically review the thinking, planning, and detailed results of sequential stages of the project. Phase 1 (1957 to 1965) was a feasibility study involving data collection from more than 6,000 patients. In phase 2 (1963 to 1970), 1,000 patients were randomized into four treatment groups: bed rest, drug-induced hypotension, carotid ligation, and intracranial surgery. In phase 3 (1970 to 1972), 242 new patients were randomized into three