AbstractThe principal imaging devices used in clinical and research medicine are mentioned with a more detailed discussion of the instruments used in clinical practice and the modified devices presently in operation at Donner Laboratories. Radionuclide imaging techniques have become remarkably sophisticated since the first mechanical scanner was introduced 20 years ago. Today, high‐resolution scintigrams can be produced in minutes, and sequential images, each requiring only a few seconds, provide data on blood flow distribution and organ function. Tomographic imaging has further extended the capability and reliability of organ imaging.