The present chapter is structured as follows: A brief overview of the importance of measuring the flows of tourism trips and visitors is succeeded by a review of the general measurement issues underlying tourism flows (sect. B). The remaining sections provide and extensive discussion on how to collect data on inbound, domestic and outbound tourism. Section C discusses inbound tourism, with a special focus on tourism as an internationally traded service, and both proposes a two‑phased approach for measuring global flows and studies their characteristics in depth. Section D considers domestic tourism, centring on household surveys as the dominant information source, and examines some of the factors that affect statistical design and sampling. Section E, on outbound tourism, draws heavily on the content of the preceding two sections. Sections C to E each conclude with a proposed table of results.