Background and Purpose— Spontaneous idiopathic subarachnoid hemorrhage (SAH) with a perimesencephalic bleeding pattern is usually associated with a benign course, whereas a diffuse bleeding pattern has been associated with a higher risk of vasospasm and disability. We evaluated whether volume of bleeding explains this disparity. Methods— Pattern and amount of bleeding (by Hijdra and intraventricular hemorrhage scores) were assessed in 89 patients with nonaneurysmal SAH. Outcomes included angiographic vasospasm, delayed cerebral ischemia, and functional outcome at 1 year. Results— Diffuse bleeding was associated with significantly higher Hijdra and intraventricular hemorrhage scores than perimesencephalic SAH, P ≤0.003. Angiographic vasospasm was more likely in diffuse versus perimesencephalic SAH (45% versus 27%; odds ratio, 2.9; P =0.08), but adjustment for greater blood burden only partially attenuated this trend (adjusted odds ratio, 2.2; 95% confidence interval, 0.69–7.2; P =0.18); delayed cerebral ischemia was only seen in those with diffuse bleeding. Patients with diffuse bleeding were less likely to be discharged home (68% versus 90%; P =0.01) and tended to have more residual disability (modified Rankin scale, 3–6; 20% versus 6%; P =0.18). Conclusions— Nonaneurysmal SAH can still result in vasospasm and residual disability, especially in those with diffuse bleeding. This disparity is only partially accounted for by greater cisternal or intraventricular blood, suggesting that the mechanism and distribution of bleeding may be as important as the amount of hemorrhage in patients with idiopathic SAH.