More than one million people died in Cambodia from 1975 to 1979 under the regime of the Khmer Rouge. Thirty years later, a Cambodian court supported by the UN tries to hold legally accountable those most responsible for the crimes committed. This study presents some of the major legal issues relevant to possible genocide charges against the Khmer Rouge at the Extraordinary Chambers in the Courts of Cambodia. In a first part, the basic structure and elements of the crime of genocide under International Criminal Law are looked at, with a focus on the particular intent requirement and the issue of groups as targets of genocidal intent. The second part of the study examines the case of the Khmer Rouge mass atrocities based on the legal framework elaborated, discussing questions involved in the legal characterization of Khmer Rouge policies. These questions include the auto-genocide debate, the distinction between discriminatory mass killings and genocidal intent as well as the legal relevance of motives for group targeting.