A simulated body fluid (SBF) with ion concentrations similar to body fluid, proposed by Kokubo et al., is widely used to evaluate bone-bonding potential through the formation of an apatite layer. To be confident of the evaluation of the potential for the apatite formation in SBF, standard substrates are required. Although Na(2)O-CaO-SiO(2) glasses have been focused upon as candidate standard substrates, it has not been clarified whether the preparation conditions of the glasses affect their apatite formation potential in SBF. In this study, Na(2)O-CaO-SiO(2) glasses were prepared by a conventional melting-quenching method with different melting periods and annealing processes to examine their properties, including apatite formation in SBF. The Na(2)O-CaO-SiO(2) glasses show reproducible apatite-forming ability when prepared using moderate melting and annealing processes, and can be useful substrates to test the reproducibility of SBF.