This document discusses various tools for measuring corruption from theoretical and practical perspectives. It describes experts' assessments, composite indices, sample surveys on experiences of corruption, and service delivery surveys as common approaches. Experts' assessments are relatively inexpensive but rely on individual perceptions, while composite indices synthesize different data but may lack policy-making usefulness. Sample surveys can investigate how corruption occurs and its impacts, targeting individuals, businesses, or civil servants. Service delivery surveys give consumers a voice and provide unambiguous data for monitoring reforms over time. Other examples discussed are the Council of Europe's comprehensive monitoring approach.