The selection of materials for control of nuclear reactors employing a variety of coolants and working over a broad range of neutron spectra are considered from a qualitative standpoint. The materials discussed include hafnium, boron, cadmium, indium, silver, europium, gadolinium, and samarium. A basis for selection of materials is presented which should permit control of practically any reactor proposed today with a minimum of additional development. Materials are discussed from the standpoint of nuclear acceptability, metallurgical fabricability, corrosion resistance, radiation damage resistance, economics, and probable contributions to the over-all radioactivity problem.