The clinical and neuropathological features of 84 nonsurvivors of aneurysmal subarachnoid hemorrhage (consecutive autopsy series) were compared with those of 51 survivors (consecutive clinical series). The groups differed significantly in the type of bleeding: 58% of the nonsurvivors had massive subarachnoid hemorrhage (MSAH) compared to 10% of the survivors (P < 0.00001); 54% of the nonsurvivors had intraventricular hemorrhage (IVH) compared to 29% of the survivors (P < 0.008); 45% of the nonsurvivors had intracerebral hematoma (ICH) compared to 8% of the survivors (P < 0.00001). Only 1 of the 19 patients with both MSAH and ICH survived. The incidence of cerebral infarction was similar in nonsurvivors (31%) and survivors (29%). In the absence of associated MSAH, IVH, or ICH, cerebral infarction was uncommon (11%). Documented in-hospital rebleeding was uncommon in nonsurvivors (13%) and survivors (2%). Admission neurological status did not predict outcome independent of the extent of the initial bleeding. Comparison of the two groups suggests that the type and extent of initial bleeding are the most important determinants of mortality in aneurysmal subarachnoid hemorrhage.