Evaluations of programmes and interventions financed through the European Social Fund (ESF) have proven challenging and have in many cases not allowed policy-makers to draw evidence-based conclusions regarding their effectiveness and efficiency. In order to strengthen future evaluations, the European Commission is encouraging Member States to increase efforts to develop credible evidence of ESF effects beyond what would have been achieved in the absence of ESF support. Such evidence requires counterfactual impact evaluations (CIEs) – i.e. comparison of results to estimates of what would have occurred otherwise. This guidance provides practical advice on some of the key questions that need to be considered when designing, commissioning and conducting CIEs. It is intended for ESF Managing Authorities (MA) and other bodies responsible for the implementation of ESF-funded programmes and interventions. The focus is on practicalities, though through necessity some technical issues are discussed. This publication is available in electronic format in English. French and German versions will be available in October 2013.