Enhanced bioactivity has been observed for amorphous CaO-SiO(2) sol-gels with 30mol% CaO, and several structural techniques have recently been used to investigate the structural basis for this bioactivity. The current work presents the first detailed atomic model of (CaO)(0.3)(SiO(2))(0.7) sol-gel after heat treatment at 600 degrees C, produced using molecular dynamics. The model contains 1056 atoms in cubic box with length 24.1 angstrom, and specifically incorporates hydroxyl groups which are characteristic of the sol-gel. The model is in good agreement with experimental X-ray and neutron diffraction results. Inspection of the model shows a network of SiO(4) tetrahedra with an average connectivity of approximately 3. Ca have coordination of N(CaO)=5.3, in agreement with experimental results. On average, each Ca is surrounded by 4 other Ca, and visual inspection shows several large clusters of Ca. These clusters should influence the dissolution of Ca, and hence the bioactivity of (CaO)(0.3)(SiO(2))(0.7) sol-gel.