A list is provided of hermatypic coral species from 24 locations in the Indian Ocean and its peripheral seas and gulfs. Six sites are newly reported or expanded accounts, and eighteen are derived from recent literature. This is intended : (1) to provide in one place, a uniform compilation of coral species from different areas and from many diverse accounts; (2) to apply synonyms to all sites in a consistent way for the first time, so that ; (3) regional analysis at species level is possible. Synonyms are taken mainly from two recent taxonomic series, but because species stability is poor in some genera and authors may differ in their views on synonymy, all names are shown. The sources of data were selected to reduce problems inherent in using diverse material, and many sources themselves include compilations and synonyms of much older works. From 796 entities initially obtained, the removal of synonyms and entries named "spp" leaves 439 species. Further reduction is probably needed. Species rich sites extend across the Indian Ocean, with no westerly decline from South east Asia; the Red Sea as a whole contains the most species. Cluster analysis shows geographical groupings in the Arabian Gulf/Arabian Sea area, in the Red Sea and in the southwest and central Indian Ocean island areas. Of these, the Arabian Group is the most separate. A second analysis corrected for diversity differences also shows three clear groups: a northern one from the Red Sea to Sri Lanka which includes the Arabian group; a large southern or equatorial region; and a group consisting of the Mergui, Nicobar and Andaman islands in the Bay of Bengal.
