This book presents an accounting framework to critically review existing studies of aid's macroeconomic effects and as a basis for four country studies on Guinea-Bissau, Nicaragua, Tanzania and Zambia. This framework focuses on the impact of different types of aid on the level and composition of key macroeconomic aggregates such as imports, investment and government expenditure. The importance of the relationship between aid and policy reform is also stressed. The case studies find that aid has had a generally positive contribution, though recommendations to further improve aid impact are also given.