Composites of gelatin microspheres and injectable calcium phosphate cement were prepared to increase cement resorption and improve tissue ingrowth. To further enhance these properties, osteoinductive growth factors can be introduced into the microspheres. In this study, the in vitro release of preset gelatin microsphere/CaP composites was followed for 6 weeks by use of 125I-labelled rhBMP-2, rhTGF-β and rh-bFGF. Results for all gelatin microsphere composites showed a release curve that consisted of a small burst, followed by a sustained release. The magnitude of the sustained release was dependent on the growth factor used, and showed a slight dependency on the loading method and type of gelatin. Furthermore, no differences in release pattern or efficiency were found when growth factor concentration increased.