Infrared (IR) reflectography has been used in the study of art objects since the mid-1960's, mostly by scholars engaged in the research of early Flemish paintings. In the last several years, as more museums have acquired IR equipment, it has also served the interests of conservators and historians of various other artists and schools of painting, such as Picasso, El Greco, and Winslow Homer, among others. At the Cleveland Museum of Art, whose comprehensive collection includes objects from virtually every period of art history, the results of infrared reflectography suggest that is may be useful in the study not only of paintings from different schools, but of objects, manuscripts, and works on paper as well. The principles of infrared reflectography are described and compared with other imaging techniques.