Abstract Spiral CT is a new volume acquisition mode in x-ray computed tomography (CT) which was introduced in 1989. Anatomical ranges are scanned in continuous fashion in typically 20–60 s, images can be reconstructed in arbitrarily fine increments at any desired position within the scanned volume. We will illustrate the basic principles of scanning and image reconstruction in spiral CT and explain special features regarding image quality and patient dose. Particular attention is given to improved and new clinical applications, like lesion detection, 3D imaging and CT angiography. Spiral CT has already replaced conventional slice-by-slice CT scanning in many applications and will be the standard scan mode in future CT systems.