Atomic physics with positrons and positronium

The important effects of polarization and positronium formation in low energy positron-gas scattering are briefly discussed. Experiments which have made direct measurements of positronium formation cross sections are described. The use of positron beams to produce the positronium atoms for spectroscopic studies is mentioned and data for the 13S1-23S1 transition are presented. Methods of producing intense positron beams are discussed and some speculation is given concerning the uses of such beams in atomic physics. (author)