This volume in the series Chemical Thermodynamics provides a comprehensive review and critical evaluation of experimental data available for the chemical thermodynamics of inorganic compounds and aqueous species and complexes of technetium. The objective of the reviews in the series Chemical Thermodynamics is to provide a set of reliable thermodynamic data that can be used to describe the behaviour of the elements reviewed under conditions relevant for radioactive waste disposal systems and various geochemical environments. Data and their uncertainty limits are recommended for the formation energies, enthalpies and entropies of selected aqueous complexes, solids and gaseous compounds containing technetium. The data are internally consistent and compatible with the CODATA Key Values, as well as with the data in the earlier volumes in the series Chemical Thermodynamics. The book contains a detailed discussion of the selection procedures used