This overview is about today's radiologic diagnostic possibilities in acute stroke. Despite many improvements in MR technology, CT is still the method of choice for most of these patients. Contrary to a long existing opinion, CT is a good diagnostic instrument even in the early phase of acute ischemic stroke. In combination with the new helical CT technique [CT angiography] all important questions regarding early therapeutic decisions can be answered. New MR perfusion techniques are just on the way to clinical application. Invasive angiography is only rarely indicated in acute ischemic stroke. The diagnosis of intracerebral hemorrhage is also mainly CT-based. MR and DSA are mandatory for further evaluation of the etiology of the hemorrhage. Nowadays, DSA is not longer mandatory for the diagnosis of cerebral venous sinus thrombosis. In some patients CT is already diagnostic; the combination of different MR and MRA techniques nearly always allows a definite diagnosis or exclusion of a venous thrombosis.