After having outlined the structure of a computer-based simulation program, called HYMOSTRUC (9), which was developed to describe and predict hydration and microstructural development of cement-based materials, characteristic features of the simulation model are discussed. Attention is paid to changes in the number of particles in the early stage of hydration, the development of interparticle contacts and how this affects the rate of hydration and the effect of particle size on hydration characteristics. The correlation between strength and the amount of embedded cement, i.e., cement involved in the formation of interparticle contacts, and the influence of the w/c ratio and the curing temperature on this correlation is discussed. Calculated porosity in the matrix-aggregate interfacial zone is shown and compared with experimental results. The potential of the model to describe and predict isothermal and adiabatic hydration curves is illustrated with some examples and the accuracy of the results is discussed.