Non-dispersive x-ray fluorescence is a completely nondestructive means of analyzing works of art. No sampling is necessary. The non-dispersive x-ray fluorescence technique employs radioactive sources which serve the purpose of irradiating the surface being tested with x-rays (excitation) causing in turn the production of characteristic x-rays (fluorescence) of the elements in the path of the incident beam. This technique was first devised in a practical working form in 1966. A variation of the technique was tested to investigate its applicability to the examination of works of art -- what elements could be efficiently detected. Objects tested include a 15th century polychromed marble relief by the Master of the Marble Madonna, a 19th century oil on canvas by Lucius O'Brien, a 20th century oil on panel by Varley, a 17th century watercolor on paper by Harpignies, and a 19th century Chinese watercolor on paper.