Published online by Cambridge University Press: 14 August 2015
X-ray astronomy has, in the past year, seen the publication of the second Ariel (2A) and fourth Uhuru (4U) catalogues of X-ray sources. A number of new X-ray cluster identifications and the confirmation of several others has resulted. in this review I will briefly summarise the situation regarding identifications and, for the 2A clusters, discuss the luminosity function and the possible relationships between a number of cluster X-ray and optical properties. Superclusters have been tentatively proposed as a class of X-ray sources and I will comment briefly on recent observations of these objects. Cluster structure has been studied by the Copernicus and SAS-3 spacecraft and by a number of rocket observations with imaging X-ray telescopes undertaken by the Harvard Centre for Astrophysics. I will review the current situation regarding structural measurements. Finally I will discuss the present status of Iron line observations at 6.7 keV in cluster spectra and the estimates of Fe abundance that result from these data.