The nitride semiconductors have emerged as important and promising materials for a wide field of optoelectronic and electronic applications. LEDs based on GaN and its alloys with InN and GaN exhibit green, blue and UV high brightness emission levels which are ready to serve many indoor and outdoor applications. Combined with the available red LEDs or by using RGB phosphors they can be used for displays as well as for illumination purpose in office, at home, in automobiles, aircraft airport runways, ships etc. Blue laser diodes based on the same material systems are already available to be used for data storage on CD ROMs with densities in excess of 1 Gbite per cm2. This makes affordable high density digital information storage systems possible for a huge consumer market of movies in high picture quality on one CD ROM. Electronic devices based on nitrides and SiC are using the superior electrical properties for high power, high frequency and high temperature applications. However, this huge potential of promising material properties and fields of applications can only be used in a wide and economic manner, if several substantial deficiencies and drawback of the materials can be overcome. These relate mostly to severe structural imperfections of the crystals and epitaxial layers and especially the lack of substrates for GaN homoepitaxy. This volume gathered papers related to some of the scientific results presented during a symposium dedicated to III-nitrides which was organized by Jürgen Christen, Russell Dean Dupuis, Bernard Gil, Matthew Phillips and Akihiko Yoshikawa under the umbrella of the European Material Society, during its 2013 Spring Meeting. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)