This paper presents the current state of our knowledge about Antarctic blue ice areas. Scattered widely over the Antarctic continent yet covering only approximately 1% of its surface area, blue ice areas have some peculiar characteristics that make them of particular interest for planetary geologists, glaciologists, meteorologists, and climatologists. For instance, blue ice areas are subject to net ablation mainly by sublimation, since any accumulation is easily swept off their smooth surfaces by winds. Moreover, they are significantly warmer than their surroundings, and the wind over them is generally more gusty. An important feature of blue ice is its relatively low albedo (0.56) compared with that of snow (0.80). Blue ice is probably considerably smoother than snow (in the aerodynamic sense), with roughness lengths as low as 3¿10-6 m, which indicates that blue ice is probably the only permanent natural surface over which the air flow is mainly in the aerodynamic smooth regime. Further, since it is likely that very old ice is exposed at the surface of some blue ice areas, this ice would be of great interest for paleoclimatic studies. It has also been suggested that blue ice areas are sensitive to climate change; this would make them useful as Antarctic climate indicators because they can easily be monitored by satellite. Finally, this paper addresses several gaps in our knowledge about blue ice areas and gives suggestions for future blue ice area research. ¿ 1999 American Geophysical Union