This book describes the theoretical principals including potential modes of failures and equipment performance limitations and provides practical advice for making quality assurance (QA) measurements for clinical X-ray tubes and generators. The guidance given for making QA measurements seeks to be practical, using equipment commonly found in medical physics departments, and where possible alternative techniques are discussed along with their relevant limitations. Topics covered include general introduction, requirements for measuring instruments, evaluation of safety features, measurements of beam quality, tube output and consistency, focal spot size, specification for performances, and related ancillaries.