Information derived from monitoring the status of and trends in forest resources is a critical tool for policymakers, managers, and other environmental decision makers. Advances in forest monitoring technology, particularly in the use of remote sensing, have helped deliver higher quality information in a timelier manner than in the past. This chapter gives background information on the practical and statistical principles behind both ground-based and remote sensing-based forest measurement and monitoring, provides historical context for each, identifies information gaps and practical challenges, and proposes solutions for harmonizing the two sources of information. This is done through the use of a hypothetical forest management case study aimed at providing a conceptual framework for forest managers seeking to design forest monitoring systems. Finally, the chapter looks ahead to future research trends and suggests further reading.