Background and Purpose: The major determinants of hemorrhage in an arteriovenous malformation (AVM) include its angioarchitecture, as well as the patients age and clinical presentation. The aim of this study was to determine whether or not the risk of hemorrhage in an AVM differs based on the different clinical presentations and the initial age at diagnosis. Methods: A consecutive case series of 496 patients having a brain AVM was retrospectively analyzed. The radiological evidence of hemorrhage was established in 84 of these cases after the initial diagnosis of AVM had been made. These cases were analyzed using univariate analysis and Kaplan-Meier curves with respect to age at diagnosis, the clinical presentation of patients harboring the AVM as well as the Spetzler-Martin grade of the AVM. Results: Hemorrage occurred in 84 patients with an AVM during a mean duration of 2.5 years (range, 1month-28 years). In univariate analysis, a subsequent hemorrhage within an AVM was associated with the following factors: When the patients initially presented with a hemorrhage, and, had a younger age (< 30 years), female gender, and Spetzler-Martin III and IV grades. By analysis of the Kaplan-Meier curves, it was estimated that the annual hemorrhage rate was 12.3% in those cases who initially presented with hemorrhage, compared with 3.5% for those cases whose initial presentation was not associated with AVM bleed. In the latter category (i.e., patients who did not have hemorrhage as the initial presentation), the annual rate of subsequent hemorrhage was lower for those patients who initially presented with seizures than those who had other initial presentations (such as those having neurological deficits, headaches, or those incidentally detected to be having an AVM) (with the bleeding rate being 1.9% in those with seizures as the initial presentation vs. 4.6% for the other presentations or those with incidentally detected AVMs, P = 0.002). Conclusions: The subsequent occurrence of hemorrhage in an AVM was associated with the initial presentation of hemorrhage, a younger patients age (< 30 years), the female gender, and Spetzler-Martin grades III and IV. The risk of subsequent hemorrhage in patients with an initial presentation of a seizure was lower than the risk of hemorrhage that occurred with other presentations. Patients with an AVM who present with recurrent headaches, and those in whom the AVM has been detected incidentally, should also be kept under surveillance as they too manifest a risk of a subsequent hemorrhage.