This chapter gives a brief description of medical imaging tests and other tests routinely used at a major health care institution. Diagnostic imaging plays an extremely important role in the overall care of the patient, including diagnosis, staging, and monitoring of the patient during their stay in hospital. Some of the examples in this book are taken from diagnostic imaging studies for cancer, however, there are many other ways to perform diagnoses, and some of these will also be explained. In addition to cancer, medical tests for heart disease and stroke will be described, as well as some medical tests for diagnosing diabetes and infectious diseases. Most of the medical tests described in this chapter will appear in the many examples to follow in later chapters.