The dramatic bleaching events on the coral reefs recently have enhanced the need for environmental monitoring. Remote sensing is an important constituent for monitoring of reefs, and an invaluable complement to field observations. This paper discusses the possibilities and limitations of present high resolution satellites for mapping and monitoring coral reefs. The sensors with the best spatial and radiometric resolution available today, e.g. IKONOS, can be useful for mapping and monitoring of reefs, but they are too costly for global surveys. However, our coral bleaching studies indicate that massive bleaching could be detected even from satellites with lower resolution, like Landsat, SPOT, and IRS. They could also be useful for coarser, from a spatial and thematic point of view, global mapping and updating purposes. A more detailed monitoring requires both better spatial resolution and spectral resolution than today's sensors. In the future, it is necessary to construct a more reef specific sensor with a few specially selected narrow bands and a good spatial, radiometric and temporal resolution.