Abstract ISO 15708-1 provides a tutorial introduction to the theory and use of computed tomography. It begins with an overview intended for the interested reader possessing a general technical background. Subsequent, more technical clauses describe the physical and mathematical basis of CT technology, the hardware and software requirements of CT equipment, and the fundamental measures of CT performance. This part of ISO 15708 includes an extensive glossary (with discussions) of CT terminology and an extensive list of references to more technical publications on the subject. Most importantly, this part of ISO 15708 establishes consensus definitions for basic measures of CT performance, enabling purchasers and suppliers of CT systems and services to communicate unambiguously with reference to a recognized standard. It also provides a few carefully selected equations relating measures of CT performance to key system parameters. ISO 15708-1 gives guidelines for, and defines terms for addressing the general principles of X-ray CT as they apply to industrial imaging. It also gives guidelines for a consistent set of CT performance parameter definitions, including how these performance parameters relate to CT system specifications.