This review will summarize current positron research at Lawrence Livermore National Laboratory(LLNL) using high-energy positron beams. We are combining positron lifetime and orbital electron momentum spectroscopic methods with theoretical simulations to provide a better understanding of positron annihilation behavior in materials. Topics covered include correlation of positron annihilation characteristics with structural and mechanical properties of bulk metallic glass and compositional studies of embrittling features in reactor pressure vessel steels. (C) 2002 Elsevier Science B.V All rights reserved.