The diagnosis of cerebral aneurysm is currently based on the angiographic data. We have tried to evaluate the usefulness of a less-invasive examination, such as the dynamic-CT, in the diagnosis of intracranial aneurysm and of the possible and concomitant subaracnoid haemorrhage. The CT examination is useful in the diagnosis of both subarachnoid haemorrhage and giant trombosed aneurysm. It is less reliable than the angiography as regard to aneurysm of small dimension.