Light reflected from the Earth's surfacecan be describedin terms of its intensity and polarization and yet remote sensing has concerned itself with the measurement of intensity and has paid little attention to the measurement of polarization. In this review, imaging and non-imaging systems for measuring the state of polarization of reflected light are described, together with their associated problems. Field and laboratory measurements of the polarizingeffects of minerals, soils, vegetation, water and oil slicks are presented. It is recommended that future research could concentrate upon, first, establishing the precise relationships between polarization and surface factors such as moisture content, roughness, particle size and albedo and, secondly, the methods by whichpolarization imagery could be collected, processedand displayed.