An accurate etiological diagnosis of spontaneous intracerebral hemorrhage (ICH) needs to be determined expeditiously because of the multiple potential causes and corresponding treatments. The diagnostic testing includes the presence of an associated headache, a history of trauma (physical or psychological), a history of hypertension, recent cognitive decline, use of anticoagulants or thrombolytics, heavy alcohol use, illicit drugs, and hematological disorders. This chapter provides an algorithm for laboratory and other ancillary testing in the diagnosis of spontaneous intracerebral hemorrhage. An estimate of the hematoma volume on computed tomography (CT) or magnetic resonance imaging (MRI) is very useful in predicting the clinical course and in guiding management decisions. Cerebral angiography is the most sensitive study for cortical veins and cavernous sinus thrombosis. Cerebral angiography may show a beading pattern in multiple medium-sized and small intracranial arteries caused by focal concentric narrowing in the distal vasculature.