Coral reefs are the most spectacular and diverse ecosystems in the marine environment. Over the last decades, however, dramatic declines of coral reef communities have been observed. Based on an international meeting on "Coral Health and Disease" in Eilat, Israel in April 2003, the book starts with case studies of reefs. The second part on microbial ecology and physiology describes the symbiotic relations of corals and microbes, and the microbial role in nutrition or bleaching resistance of corals.