This little volume is intended to assist the medical profession and roentgen technician in the purely technical aspect of the science. It should be of particular value to beginners. The matter is discussed from the standpoint of the author's personal experience with his foreign equipment. While the underlying physical principles for obtaining good exposures are identical, the American roentgenologist and technician would experience occasional difficulty in readily converting the data into the form employed in American practice even though he is familiar with the German language. The author refrains from a discussion of purely diagnostic matters. His observations pertain to a large variety of x-ray apparatus—all of German and Austrian make— the comparative efficiency of which appears in tabulated form. The subject is discussed with reference to films as well as to therapy. The first two chapters deal solely with the physical principles that govern the production of the ray.