Background and Purpose: With its highly variable clinical presentation, the diagnosis of cerebral venous sinus thrombosis (SVT), and especially of deep venous thrombosis (DVT), as rare but important causes of stroke is challenging. Because noncontrast cranial CT (NCCT) is still the imaging technique of choice in most emergency departments, we aimed to investigate its value in the diagnosis of SVT and DVT. MATERIALS AND METHODS: Screening our patient data base, we identified 8 patients with DVT and 25 patients with SVT. We also included a control group of 36 patients who had presented with clinical signs of DVT or SVT but in whom thrombosis was subsequently excluded. MR imaging, multidetector row CT angiography (MDCTA), and/or digital subtraction angiography (DSA) were used as the reference standard. Three independent readers assessed the NCCTs for the presence of direct and indirect signs of DVT or SVT. Direct signs included the presence of hyperattenuated sinuses (ie, cord sign) or veins (ie, attenuated vein sign), whereas parenchymal edema and hemorrhage were indirect signs. Results: The sensitivity and specificity of the attenuated vein sign for the diagnosis of DVT were 100%, and 99.4%, respectively, whereas the sensitivity and specificity of the cord sign for SVT were 64.6% and 97.2%, respectively. The sensitivity and specificity values of NCCT were 93.7% and 98% for intracerebral edema and 94.8% and 98.7% for intracerebral hemorrhages, respectively. Conclusions: Although NCCT is insufficient to exclude a SVT, its value in the emergency diagnosis of DVT seems to be very high.