Subarachnoid hemorrhage (SAH) followed by cerebral vasospasm (CV) leads to severe debilitation or death of an estimated one million people worldwide every year. A biomarker that would predict the onset of CV after a SAH would be useful in informing treatment protocols, but has yet to be found. The focus of this study is to explore differences in protein phosphorylation in cerebral spinal fluid (CSF) among healthy patients, SAH patients and SAH-CV patients. A significant difference in phosphorylation among the three sample types could be an important step towards the discovery of a diagnostic marker. The identification and validation of phosphorylated protein differences for study is manifested in the nature of signaling involved in the pathological events seen post SAH. Capillary liquid chromatography (cap-LC) coupled to inductively coupled plasma mass spectrometry (ICPMS) and nano-liquid chromatography-CHIP/ion trap mass spectrometry (nanoLC-CHIP/ITMS) are used to identify and measure protein phosphorylation changes in the CSF of the aforementioned groups. ICPMS represents a suitable method for screening ultra-trace phosphorus levels at the natural isotope, ³¹P, while nano-LC-CHIP/ITMS is used to identify phosphoproteins by searching appropriate protein databases.