The main achievements of Pseudo-Hermitian Quantum Mechanics and its
distinction with the indefinite-metric quantum theories are reviewed. The issue
of the non-uniqueness of the metric operator and its consequences for defining
the observables are discussed. A systematic perturbative expression for the
most general metric operator is offered and its application for a toy model is
outlined.Comment: 5 pages, Contributed to the Proceedings of the 3rd International
Workshop on Pseudo-Hermitian Hamiltonians in Quantum Physics, June 20-22,
2005, Koc University, Istanbul, Turke
