The bioactivity of bioactive glasses is related to their dissolution in the presence of body fluid, or water. The dissolution process involves disruption of the tetrahedral network structure through the formation of silanol groups on the take-up of water by bioactive glasses. Molecular dynamics simulations show that the dissolution energy varies considerably depending on the nature and environment of the Si-O-Si bond being broken. However, no obvious correlation with bioactivity is observed, suggesting that although the network disruption is a necessary process, it is not rate determining. (c) 2006 Published by Elsevier B.V.