We present a review on mercuric iodide technology for room temperature gamma radiation detection. After four decades of research and development the material is attractive for a number of applications for x-ray and gamma-ray imagers with performances that match all competing materials. The crystal growth of large single crystals is challenging; however the high resistivity of 10(13) Omega cm, the undoped, as-grown crystals and the high radiation damage remaining features that are not exhibited by any other wide bandgap semiconductor materials. (c) 2013 Elsevier B.V. All rights reserved.