Peace and conflict have at last successfully entered the mainstreaming agenda of development donors and agencies. Over the past couple of years the community of researchers and practitioners has been developing better policy and operational approaches and and tools for better working for and in zones of violent conflict or in the aftermath of violent conflict or wars. While the aid community has become much more aware of the need to “Do No Harm” by working “conflict sensitively,” the peace community has only just started looking into more effective ways and means of contributing to peacebuilding methods more effectively by evaluating peace efforts. The debate on conflict sensitivity has started in the mid 1990s as a highly political issue aiming at preventing armed conflicts, such as the genocide in Rwanda in 1994, through effective international preventive measures. However, during the last decade we have seen development donors and agencies moving more into a tool-based approach on the program level of interventions. Today we find a variety of different tools, often disconnected from the overall political conflict/peace situation, thereby limiting the effects of conflict-sensitive work. This article gives an overview of the topic of conflict-sensitive development and aims at contributing to a better understanding of what “conflict sensitive development” is all about. The article explains why working in situations of violent conflict is different from “normal” development circumstances, presents a short history of the debate on around conflict-sensitive development, and shows how terms such as “Do no harm ,” PCIA , and “conflict sensitivity” are often used and confused. The article also goes into the practice of conflict-sensitive development on both the political and the program level, and presents good and bad practical examples and a list of challenges ahead.