Positron annihilation is a sensitive technique for probing defects in metals and it has recently been shown to be a valuable tool for the study of radiation damage. After an introduction to the three basic experimental methods (angular correlation,Doppler broadening, and lifetime measurements), the interaction of positrons with lattice defects is reviewed. Results for the annealing of damage after low‐temperature irradiation are used to show that positron annihilation has provided new information on annealing kinetics. The role of positron techniques in characterizing complex defect structures resulting from high‐temperature neutron irradiation is reviewed and the possible utility of positron annihilation as a nondestructive monitor of property changes is pointed out.