This study is part of the Peace Support Operations project, commissioned by the Swedish Ministry of Defence. The project supports the Ministry with research regarding a wide range of areas with relevance for peace support operations. This includes e.g. civil-military relations, Security Sector Reform and evaluations of past and current operations. The aim of this study is to examine negative unintented consequences of Peace Support Operatons (PSOs) and present recommendations on how to manage these. The study is based on a review of previous reports as well as policy documents (primarily from the UN) on mitigating negative unintended consequences of PSOs on host countries. Particular attention is given to four areas: impact on host economies, sexual exploitation and abuse, the contribution to the spread of HIV/AIDS and environmental degradation. The report explores how these types of negative unintended consequences have been dealt with by the UN. Attention is also given to current Swedish practices. The report finally presents some concluding remarks and recommendations for how to improve future PSOs by addressing the prevalence of unintended consequences. While the recommendations have been developed primarily with a Swedish context in mind, the report presents issues of relevance to other troop contributing countries as well.