[en] Positron annihilation is a new addition to the techniques capable of furnishing microscopic information on defects in semiconductors. The present state of the art of annihilating positrons will be briefly reviewed. Recent high temperature measurements on silicon will be discussed in detail with the aim of demonstrating the capabilities of this method as well as demonstrating the kinds of assumptions necessary for arriving at numerical values for, say, vacancy formation enthalpies. The consequences of the positron annihilation experiments on diffusion mechanisms will also be considered. (author) 5 figs., 35 refs