This paper reviews the role of food aid in response to humanitarian emergencies. It outlines a set of basic principles for effective food aid interventions, and analyses a number of case studies in humanitarian response. The paper distinguishes between rapid onset and slow onset emergencies and between 'idiosyncratic' emergencies affecting individuals or households and 'covariate' emergencies affecting entire communities or countries. The lead-time afforded by slow-onset emergencies could be ' but usually is not ' used to mount early interventions aimed at averting full-scale disasters. Emergency response is too heavily dominated by food aid, especially aid sourced in donor countries, to the neglect of more effective and less costly interventions. What's more, idiosyncratic shocks are usually overlooked in humanitarian response. The paper draws a number of 'lessons learned' from recent experience with different types of humanitarian emergencies. It argues that emergency food aid is often a necessary part of humanitarian response to acute food insecurity, but it is rarely sufficient.