Evaluation of the impact and effectiveness of general budget support: Finnish support to Mozambique The Paris Declaration commits both donors and recipients to hold each other accountable for the effectiveness of aid. In this context, general budget support (GBS) has been promoted as the most suitable form of aid for fulfilling commitments made under the declaration. The article examines the challenges faced in evaluating the effectiveness and impact of Finnish GBS to Mozambique. The evaluation of GBS is approached focusing on three elements of the theory of change behind the programme: setting the boundaries of GBS, identifying various interpretations of ‘mutual accountability’, and assessing the coherence and relevance of the outcomes chain for reducing poverty. The data consist of international and national documents dealing with the efficiency of aid and the relevant research literature. The results show that the theory of change behind GBS includes complex elements and presuppositions, some of which are implausible or plausible only under certain conditions. If the evaluation of GBS is restricted to monitoring technical indicators, it will ignore factors that are important for achieving the intended outcomes. At the same time, political developments in both countries have eroded the basis for cooperation. Keywords: Development cooperation, effectiveness of aid, evaluation, mutual accountability, direct budget support, theory of change, Finland, Mozambique.