Quantum electrodynamics of weakly bound systems

An overview of quantum electrodynamic effects in two-body systems is presented. Recent advances in the calculation of the hydrogen Lamb shift, muonium hyperfine structure, and positronium energy levels are described in detail. The comparison of experimental results to current theoretical predictions gives agreement in most cases. However, a few significant discrepancies remain, which indicates the necessity for further refined calculations and measurements. This revised version was published online in July 2006 with corrections to the Cover Date.