We evaluated the possibility of improving detection of a dense intracranial artery on CT in acute stroke by narrowing window width, varying window level and performing a thin-slice helical scan for the circle of Willis, in some cases followed by postprocessing maximum-intensity projections. We carried out 32 examinations of 31 patients with a documented cerebral ischaemic attack, performing cranial CT within 6 h of the onset of symptoms. Patients with intracranial haemorrhage were excluded, as were patients who went on to thrombolytic therapy. Varying window width and centre level on standard 5 mm thick contiguous axial slices, we detected a dense proximal middle cerebral artery (MCA) in a higher proportion of patients. A 1.1 mm thick helical scan through the circle of Willis improved recognition of a dense distal horizontal segment and the temporoinsular branches of the MCA and of a dense posterior cerebral artery.