In order to provide representative measurements of wind speed and direction, measuring devices must be deployed in suitable locations or sites and the instruments themselves exposed to the wind they are intended to measure in a standardised manner. This chapter sets out what those standardised conditions of site and exposure are for measurements of wind speed and direction, including the treatment of wind gusts and construction of the vector mean wind, following the guidelines laid down by the World Meteorological Organization in the so-called CIMO guide (Commission for Instruments and Methods of Observation). Well-exposed sites can be difficult to find, and optimal exposure conditions for wind instruments differ considerably from most other meteorological instruments. Instruments to measure both wind speed (cup and sonic anemometers) and wind direction (wind vanes and sonic anemometers) are covered, with their limitations, together with a description of the Beaufort wind scale, which is useful if suitable instruments (or a suitable site for them) are not available.