This brief reviews the Integrated Food Security and Humanitarian Phase Classification (IPC). This is a system for defining the severity of a situation (from 'generally food secure' to 'humanitarian catastrophe'), based on a wide range of indicators of the impact of hazard events on human health and welfare. The IPC is being seen as a major step forward in improving food security information systems and response mechanisms to addressing hunger and vulnerability. However, it also has a number of significant weaknesses which need to be addressed before it can be rolled out.