A statistical relationship is derived between sea surface winds and the brightness temperatures, T sub B, measured by the Nimbus 5 Electrically Scanning Microwave Radiometer ESMR in cloudless areas. The relationship is derived by using wind observations in the Mistral and the Tehuantepecer, two fall wind situations occurring in very different sea surface temperature and atmospheric water vapor environments. The Mistral, off the coast of southern France, is characterized by relatively cold sea-surface temperatures of 12 to 15C and dry atmospheres with about 1 cm. of precipitable water. The Tehuantepecer, off the Pacific coast of southern Mexico is characterized by warm sea surface temperatures of 22 to 28C, and moist atmospheres with about 3 cm. of precipitable water. The data thus provided a wide range of sea surface temperatures and atmospheric water content for deriving an equation relating wind and T sub B. The derived equation expresses the surface winds in terms of T sub B, sea surface temperature, and atmospheric water content, and fits the data with a probable error of 5.1 knots. The equation is used to estimate winds over the western Atlantic during an outbreak of polar air which produced strong winds.