Since 20 years, calcium phosphate compounds are used as bone substitutes.In this study, three commercial ß-TCP preparations (Cerasorb, Bioresorb and Biovision) were examined in regard of their crystallinity (scanning electron microscopy), external porosity (section preparations) and chemical composition (x-ray-difractome-try). REM-pictures show significant differences in the crystallinity of the three preparations. These results were confirmed by testing the compressive strength of single particles. With a value of 5 N, Cerasorb showed the maximum stability, which is indeed about 20 times lower than that of bone. The external porosity of the material in the erosion is crucial for the process of bone growing in. In this regard, the preparations showed no significant differences. Their median values varied in a range between 40 to 58%. By the help of x-ray-difractometry, aside from the main component Ca3(PO4)2 (whitokit synth.), contaminations were discovered in all three preparations. The contaminations formed phases with concentrations under 0,5%. In Cerasorb, phases of CaH2P2O7 and CaH2P2O5 were detected. Bioresorb was contamined with phases of Ca3(PO4)2 x H2O, Ca5(PO4)3(OH), Ca2P2O7 and CaHPO4 x 2H2O. The purest preparation was Biovision with the two contamining phases Ca2P2O7 and Ca5(PO4)3OH in a concentration less than 0,2%. Among all examined preparations, Cerasorb showed the best crystallinity. The preparations did not differ in regard of their external porosity. Non of the preparations is free from contaminations. The existence of contamining phases indicates, that technological parameters in the production process of ß-tricalcium phospate hinder the complete crystallisation of whitokit. The biological significance of contaminations in ß-TCP should be investigated in histological and clinical studies. Schlagwörter: beta-Tricalciumphospates, beta-Tricalciumphospates