OBJECTIVE Nontraumatic subperiosteal orbital hemorrhage (NTSOH) has been reported rarely in association with sudden elevation of cranial venous pressure, generalized diseases with bleeding diatheses, and paranasal sinusitis. To define more clearly the clinical and imaging characteristics of NTSOH, we evaluated nine cases seen by the authors and reviewed previous case reports. METHODS Retrospective, noncomparative case series. METHODS Nine patients (10 eyes) with NTSOH. METHODS All patients underwent computed tomography scans of the orbits. Patients with typical clinical and imaging features and normal visual function were observed. Those with an uncertain diagnosis or visual compromise underwent surgical drainage of the hematoma. METHODS Resolution of proptosis, diplopia, lid swelling, and ptosis. RESULTS Nine patients ranging from birth to 73 years of age were identified. All were females. The lesions were located superiorly in eight patients (one patient had bilateral lesions) and medially in one patient. Most were associated with sudden elevation in venous pressure (vomiting, strangulation, straining), and most required no surgical intervention. The bilateral case occurred in the setting of disseminated intravascular coagulation and was the only case associated with visual loss possibly resulting from ischemic optic neuropathy. CONCLUSIONS Nontraumatic subperiosteal orbital hemorrhage may occur at any age, usually secondary to sudden elevation in venous pressure. It is nearly always superior. The clinical and radiologic features are sufficiently characteristic to allow conservative treatment in the absence of visual compromise.