Human osteoclasts derived from CD14+ precursors were cultured on discs of stoichiometric hydroxyapatite (HA) and carbonate substituted hydroxyapatite (CHA) of varying carbonate contents. Resorption of the ceramic increased with increasing carbonate content up to 2.35 wt. %. Development of osteoclasts is qualitatively different on ceramics compared to dentine, occurring in discrete, confluent subpopulations, which suggests local cell signalling may be important in the process. Resorption appears to drive further development of osteoclasts. Controlling carbonate content may be one way of controlling the rate of resorption of synthetic HA ceramics.