This volume is part of the series on "Chemical Thermodynamics", published under the aegis of the OECD Nuclear Energy Agency, and updates and expands the thermodynamic data on inorganic compounds and complexes of uranium, neptunium, plutonium, americium and technetium contained in the previous volumes of the series. A review team, composed of seven internationally recognized experts, has critically reviewed during five years all the scientific literature containing chemical thermodynamic information for the above mentioned systems that has appeared since the publication of the earlier volumes. The results of this critical review carried out following the Guidelines of the OECD NEA Thermochemical Database Project have been documented in the present volume, which contains new tables of selected values for formation and reaction thermodynamical properties and an extensive bibliography.