Alteration in the chemical composition of a biomaterial may be undertaken to improve its biological properties. The aim of this work was to evaluate the biocompatibility of three chemical compositions of Ricinus communis polyurethane (RCP): RCPp (pure RCP), RCP + CaCO(3), and RCP +Ca(3)(PO(4))(2). RCP cylinders were surgically implanted in rabbit femurs. After 8, 12, and 16 weeks, the femurs were removed, fixed, sectioned, ground, and stained by Stevenel's blue/Alizarin red S for light microscopy and histomorphometry. The osseointegration and osseoconductivity were calculated by means of image analysis and the data were submitted to the Kruskal-Wallis test followed by Dunn's test. Osseointegration was already completed after 8 weeks on RCP + Ca(3)(PO(4))(2) because similar values were found from week 8 to 16, whereas it showed a time-dependent increase on RCPp and RCP +CaCO(3). The osseointegration was greater on RCP + Ca(3)(PO(4))(2) in all periods when compared with RCPp, and after 8 and 12 weeks when compared with RCP + CaCO(3). None of the RCP samples presented osseoconductivity. The present results showed that RCP blended with calcium phosphate improved the biocompatibility by both enhancing and accelerating its osseointegration. Based on the absence of osseoconductivity, RCP was considered to be a bioinert material.