Serial spectrophotometric scans of cerebrospinal fluid (CSF) and computed tomographic (CT) scans of 99 patients with a subarachnoid hemorrhage (SAH) were examined. The xanthochromic index (i.e., the sum of the absorption values at 416 nm (oxyhemoglobin) and 460 nm (bilirubin)) yielded an accurate diagnosis in 82%, as did the CT scan. When both spectrophotometric and CT scans were used, the accuracy of SAH diagnosis increased to 96%. The xanthochromic index was valuable in estimating the date of hemorrhage and also correlated well with the clinical outcome of these patients. Only 42% of the recurrent hemorrhages were diagnosed by CSF spectrophotometry; in this capacity, its role seems less clear. However, a positive diagnosis of recurrent hemorrhage by CT scan was made in 83%.