One of the enduring concerns of moral philosophy is deciding who or what is deserving of ethical consideration. This special issue of Philosophy and Technology investigates whether and to what extent machines, of various designs and configurations, can or should be considered moral subjects, defined here as either a moral agent, a moral patient, or both. The articles that comprise the issue were competitively selected from papers initially prepared for and presented at a symposium on this subject matter convened during the AISB/IACAP 2012 World Congress, held in at the University of Birmingham in Birmingham, UK.