Symposium U, "Nuclear Radiation Detection Materials," held April 26-28 at the 2011 MRS Spring Meeting in San Francisco, California was a continuation of the 2009 symposium and provided the latest research in nuclear radiation detection materials. Types of detector materials include semiconductors and scintillators, which are represented by a variety of new scintillator materials; novel semiconductors; and traditional detection materials. There is a strong need for new materials and methods for a variety of radiation detection applications in this rapidly growing field. The symposium gave an overview of the crystal growth of radiation detector materials and the characterization and technology issues and moved on to discuss several important improvements for the development of future radiation detectors.