BACKGROUND: Here, we compare the angiographic characteristics of hemorrhagic and nonhemorrhagic hemispheres within the same adult patient with moyamoya disease (MMD) and identify the possible risk factors for initial and recurrent hemorrhage during the long-term follow-up period. METHODS: We retrospectively collected and analyzed the clinical and angiographic data of 145 consecutive adults with hemorrhagic MMD between 2004 and 2011. Separate angiographic characteristics of the hemorrhagic and nonhemorrhagic hemispheres were analyzed based on digital subtraction angiography. Multivariate logistic regression analysis was used to study the risk factors related to initial hemorrhage. In addition, clinical follow-up for at least 5 years was obtained in all the 145 patients. Cox regression analysis was used to determine the predictors for the subsequent recurrent hemorrhagic strokes. RESULTS: With regard to the 145 consecutive patients in our cohort, multivariate analysis indicated that the dilation grade of anterior choroidal artery (odds ratio [OR], 2.449; 95% confidence interval [CI], 1.617-3.862), the dilation grade of the posterior communicating artery (PComA) (OR, 1.491; 95% CI, 1.071-2.075), and the involvement of the posterior cerebral artery (OR, 4.623; 95% CI, 1.273-16.792) were significantly associated with initial hemorrhage. After a median follow-up of 6.33 +/- 1.81 years, 20 of the 145 patients (13.8%) developed 22 recurrent episodes of hemorrhage. No significant correlation was found between rebleeding and the above significant factors associated with the initial hemorrhage. CONCLUSIONS: Compared with the nonhemorrhagic hemispheres, hemorrhagic hemispheres are more prone to recurrent hemorrhage. Our case-control study showed the dilation of the anterior choroidal artery or posterior communicating artery, as well as the involvement of the posterior cerebral artery, is associated with the initial hemorrhage of MMD, but not for the episode of recurrent hemorrhage. Longer and more detailed clinical and angiographic follow-up are still needed to delineate the specific mechanism underlying the recurrent hemorrhage in hemorrhagic MMD.