Volume III/27 covers the magnetic properties of inorganic compounds based on transition elements. It can therefore be considered as a supplement to volumes III/4 and III/12 Magnetic and other properties of magnetic oxides and related compounds, which appeared in 1970 and in the period 1978 - 1982 respectively. In a way, this volume also forms a counterpart to volume III/19, in which the magnetic properties of metals, alloys and metallic compounds are compiled. The first subvolume III/27a deals with the magnetic properties of pnictides and chalcogenides which contain 3d elements. In the present subvolume III/27d oxidic compounds with the spinel structure are treated; they include both iron and non-iron oxy-spinels. Besides the magnetic data, physical and chemical properties which are of interest in connection with the magnetism of the spinels, have been given the necessary attention. Systematic surveys help the user of this subvolume to find the substances and the properties he is interested in, and which are included in various parts of volumes III/4, III/12 and III/27.