Quantum electrodynamics of weakly bound systems

An overview of quantum electrodynamic effects in two-body systems is presen ted. 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 re main, which indicates the necessity for further refined calculations and me asurements.