The PRSP approach is the outcome of a long period of learning by the international community about how to support poverty-reduction effectively in the poorest countries. It responds to growing concerns about weak country ‘ownership’ of development policies and the negative institutional impacts of both free-standing project assistance and policy-based conditionality. The approach is best understood as a set of principles or aspirations and not as a ready-made and well-tested method. This applies to the PRSP experiment generally, and particularly to PRSP monitoring arrangements and the mechanism of the Annual Progress Report (APR), which are the main focus of the study. This report describes and analyses the challenges posed by the monitoring and evaluation of Poverty Reduction Strategy Papers (PRSPs) and budget support programmes. It draws on recent studies and surveys, and on the experience of selected donor organisations and countries, making use of documents and interviews. The main conclusion of this survey of thinking and practice in progress reviews and performanceassessment is that it is ‘unfinished business’. Neither APRs nor the supplementary monitoring mechanisms put in place by donor groups are yet effective for converting the PRSP principles into reality. But many of the actors involved are well aware of the challenges this situation poses. There are signs that progress will be made if they respond jointly to them with enough vigour and creativeness.