Azooxanthellate habitat-forming corals develop in deep waters adjacent to shallow fringing coral reefs off San Bernardo and Rosario Islands (Colombian Caribbean). This study was carried out to characterize biological and geological features of the continental margin where these azooxanthellate coral communities flourish. The principal habitat-forming corals species found were Madracis myriaster (Milne-Edwards and Haime, 1849) and other branching Madracis species. These communities rest on sandy mud bottoms over the shelf