For the last decade, and especially since the Indian Ocean tsunami, traditional humanitarian actors have worked hard to strengthen their cooperation in emergencies. The UN-led humanitarian reform resulted in the establishment of clusters for coordination of activities, the search for ways to improve humanitarian leadership and the quest for predictable and rapid financing through the wider use of pooled funds. In addition, in 2007 the UN, Red Cross and NGOs agreed on the Principles of Partnership (PoP): equality, transparency, results-oriented approach, responsibility and complementarity. NGOs are convinced that effective forms of partnership will lead to overall greater aid effectiveness, benefiting crisisaffected populations. However, is partnership between traditional humanitarian actors sufficient? What about cooperation with other civil society actors? And to what extent is partnership with donors possible? The first articles in this issue reflect on various modes of collaboration between NGOs, while other articles look into partnerships with the UN, donors and private partners.