In this project we are collecting cerebrospinal fluid and blood from patients at Vanderbilt Medical Center who have a subarachnoid hemorrhage which has followed the rupture of a brain aneurysm. We then propose to study the cerebrospinal fluid using a novel microscopic laser directed mass spectrometric analysis (MALDI) available at Vanderbilt. The cerebrospinal fluid and blood will then be analysed for different biological markers, protein expression and gene expression. These markers will then be statistically correlated with clinical data including prediction of vasospasm, time to vasospasm and response to standard therapy.