Spiral CT was performed in 9 patients with 13 cerebral aneurysms known from angiography. All lesions were detected by spiral CT, the smallest lesion measuring 3 mm in diameter. The neck of the aneurysm and the anatomical relations could be determined very accurately in all cases. Advantages of spiral CT over magnetic resonance angiography include: the short examination time, the independence of flow rate and cardiac output, and the excellent visualisation of calcification, thrombus and the bony landmarks. Disadvantages are the necessity of iodinated contrast media, the long postprocessing and reconstruction time and the possibility of overlap from bone and venous blood.