Ultraviolet microscopy has been made practical for the industrial laboratory by the advent of an RCA image-converting vacuum tube known as the Ultrascope tube, which is incorporated in Bausch & Lomh's Ultraviolet Photo-Microscope attachment. Methods of preparing samples for ultraviolet microscopical observations are generally discussed. Examples of application are given to illustrate the unique and significant information concerning polymers and fibers that can be obtained by ultraviolet microscopical tech niques.