This study, commissioned by the UK Department for International Development, reviews critically current debates regarding aid in ‘poorly performing’ countries. The study sought to clarify and make operational the concept of ‘poor performance’ by analysing the criteria against which performance is assessed, identifying the key constraints to aid engagement and developing an approach at the country level for better understanding poor performance. It has combined extensive review of relevant literatures and a statistical component with a series of desk-based country studies (India, Malawi, Rwanda and Sudan).