On coral reefs, products of bioerosion through the activity of micro- and macroboring organisms and grazers are particulate and dissolved carbonate. The contribution to bioerosion of the major boring and grazing species was estimated on French Polynesia and the island La Réunion. The influence of bioerosion on the calcification/dissolution budget of reefal waters and on particulate calcium carbonate fluxes was investigated. Studies on bioerosion were performed in order to assess: (a) eroding activity of grazers through the gut content analysis of echinoids and scarid parrot fish, (b) eroding activity of micro- and macroborers from experimental substrates exposed for one year, and (c) role of sponges in total bioerosion on reefal and experimental substrates. Calcification/dissolution budget was measured using the alkalinity anomaly technique, and particulate carbonate production was analysed from trapped sediments.