The Steiner-Lindquist laser intra-operative guidance method is described and its application in the surgical treatment of mycotic aneurysm is presented. Three illustrative cases of distal middle cerebral artery aneurysms are reported. The authors argue that all ruptured mycotic aneurysms should be treated surgically. The laser-guided stereotactic approach is presented as simple, flexible and reliable method to improve safety and accuracy of the operation in these cases. In our experience it compares favorably with previously described stereotactic techniques.