A series of ordered mesoporous SiO2−CaO−P2O5 sol−gel glasses which are highly bioactive has been synthesized through evaporation-induced self-assembly in the presence of a nonionic triblock copolymer, EO20PO70EO20 (P123), template. By keeping constant the SiO2 + P2O5/P123 ratio, the influence of the CaO precursor, Ca(NO3)2·4H2O, on the mesostructure has been determined. After calcination at 700 °C, ordered mesoporous glasses are obtained, showing structures that evolve from 3D-cubic to 2D-hexagonal when the CaO content increases. The mesoporous glasses are highly bioactive compared with conventional ones, due to the increased textural characteristics supplied by the template. The bioactivity tests point out that the surface area, porosity, and 3D-structure become more important than chemical composition during the apatite crystallization stage in these materials, due to the very high textural parameters obtained.