Objective - To estimate for the first time the incidence of subarachnoid hemorrhage (SAH) in type 1 diabetes. Research Design and Methods - Using the nationwide Finnish Diabetic Nephropathy (FinnDiane) Study cohort of 4,083 patients with type 1 diabetes (mean age of 37.4 6 11.8 years at enrollment), we analyzed the incidence of first-ever SAH events. Results - During the follow-up time of 36,680 person-years (median 9.4 years), 15 patients with type 1 diabetes experienced an aneurysmal or nonaneurysmal SAH, and thus the crude incidence of SAH was 40.9 (95% CI 22.9-67.4) per 100,000 person-years. One patient had a verified aneurysmal SAH, and four patients died suddenly of an SAH, which was most likely caused by an aneurysm. SAHs in 10 out of 15 patientswere classified as nonaneurysmal SAH, and thus the crude incidence of nonaneurysmal SAH was 27.3 (13.1-50.1) per 100,000 personyears. None of the nonaneurysmal SAHs were fatal. In univariate analysis, current smokers had a hazard ratio of 4.82 (95% CI 1.31-17.81) for nonaneurysmal SAH. Conclusions - The incidence of nonaneurysmal SAH is high among patients with type 1 diabetes. Our findings suggest that nonaneurysmal SAH is a distinct new microvascular complication in type 1 diabetes.