We studied the suitability of three different hydroxyapatite materials (Endobone, Bio-Oss and Algipore) as carriers for the bone growth promoting factor TGF-beta(1). The hydroxyapatite materials either were incubated for 24 h or directly loaded with hrTGF-beta(1) (Diagnostic Products Corporation, DPC) at a concentration of 10 ng hrTGF-beta(1)/mg. For the release experiment the hydroxyapatite materials covered with hrTGF-beta(1) were either suspended in pure phosphate buffered saline (PBS) or human serum albumin (HSA). The concentration of hrTGF-beta(1) was measured every 6 h the first day and then daily at the 2nd, 7th, 14th and 28th day. With Bio-Oss and Endobone the release of growth factor in HSA showed a two-phase kinetics. TGF-beta(1) reached a maximum concentration within the first 24 h and decreased almost linearly until day 28. With Algipore the concentration of growth factor reached a maximum after 12 h and showed a rapid decline until day 2. From day 2 the TGF-beta(1) concentrations remained low. Significantly, more TGF-beta(1) was released into HSA than into PBS. Our study suggests that the hydroxyapatite materials are suitable as TGF-beta(1) carriers.