This discussion paper developed by an inter-agency Working Group on Children without Parental Care is the outcome of an initiative launched in July 2010 to contribute to building understanding and promoting discussion about the Guidelines for the Alternative Care of Children welcomed by the UN General Assembly in December 2009. The specific aim was to move towards a common understanding of the different forms of formal care mentioned in those Guidelines. The discussion paper provides an overview of existing definitions of formal care within the UN Guidelines and a summary of the basic characteristics identified for each, together with explanations for the proposed characteristics.