In recent years a large number of intrastate conflicts have led to complex emergencies, resulting in massive human suffering. This required substantial humanitarian aid, which must be provided on the basis of the needs of the affected populations, and be based on internationally accepted humanitarian principles.The share of the total aid budget of the Netherlands spent on humanitarian assistance has increased. In the period 2000-2004 € 1.2 billion was provided for humanitarian aid, which was implemented by UN agencies, the Red Cross and Red Crescent Movement and non-govermental organisations.The amount of expenditure and the fact that humanitarian aid had not been evaluated for some time prompted this evaluation. Its major objective was to assess and document the relevance, effectiveness and efficiency of the assistance. The evaluation involved case studies in Afghanistan, Burundi and the Democratic Republic of the Congo, Somalia and Sudan; all are characterized by complex emergencies.Implementation of the evaluation proved challenging. The evaluators had to deal with a variety of practical problems such as high turnover of staff in the implementing organisations, loss of organisational memory and insecurity constraining their movement in the field. The evaluation was also hampered by the lack of detailed information on the results of aid activities.