Computed tomography (CT) is a cross-sectional imaging technique using x-rays and computers that is becoming increasingly available to veterinarians. During CT scanning, an x-ray tube rotates 360° around the patient. Multiple radiographic projections of a particular slice of tissue are made, and information from all projections is combined to create a single tomographic (slice) image. CT images provide accurate anatomic evaluation of tissue planes and regions that often cannot be visualized with conventional radiography. Whereas conventional radiographs have five radiographic opacities (metal, bone, soft tissues, fat, and air), CT systems can record thousands of separate opacities, ranging from air to high-density metal. Many imaging artifacts can occur in the process of generating CT images. A good understanding of these artifacts is necessary to enable an accurate interpretation of the CT images. After the scan examination, images in other planes can be produced using computerized reformatting, which is of help in evaluating the extent of a lesion. To increase the amount of soft tissue information, negative (air) and positive contrast agents (radiopaque iodine) can be used. Positive contrast techniques are of greatest importance for demonstrating brain tumors. Biopsies can also be obtained under CT guidance, a procedure that can be accurately performed.