Los Alamos, NM: Los Alamos Scientific Laboratory of the University of California, 1964. First Edition, First Printing thus, This Report supersedes LANL-2674, Parts I and II., Stated as 31st Edition. Wraps. x, 245, [1] pages. Printed on both sides. Figures. Tables. Formulae. Bibliography. Stapled on left side. Number on front cover. Name and organizational code in ink on front cover. Title on spine. This report is a revision of LAMS-2674, Parts I and II, to which a discussion of the nitrides and carbides of U, Th, and Pu has been added. State of the art as of mid-1960s. In general the literature covered extends from about 1930, depending on the system and the quality of the work, to March 1964. Although an effort has been made to present as complete a description of each system as possible, only that work which, in the author's opinion, would led to a clearer understanding has been discussed in any detail. Most early work and some recent measurements have been largely ignored except to show the effect of oxygen content or to give an approximate measured value when no other exists. Many of the references cited, as well as several books, contain complete bibliographies of the early literature and may be consulted when necessary. The carbides and nitrides discussed in this report suffer from two properties that have led to a considerable accumulation of questionable data. First, they are commonly single phase over a wide range of composition, and, second, they will form a solid solution with each other and with their respective oxide. Both of these factors will affect the properties of these materials, sometimes in a very striking manner. Without the use of care in preparing the compounds and the application of proper analytical techniques, an investigation may offer little meaningful information. More