A comprehensive computer based system for online prediction of mechanical properties and offline prediction of the microstructure of hot rolled C-Mn and microalloyed steel strip of has been developed. The approach used was based on two types of model: a neural model that predicts the mechanical properties and a physically based semiempirical model that predicts the microstructural features. The mechanical properties of the hot rolled strip are calculated online, but it is also possible to simulate the effects of steel composition and process parameters on the mechanical properties. The microstructural model is an offline tool for use in research and development, product planning and production. It can be applied to the study of microstructural evolution during hot rolling or to estimate changes caused by process conditions or by the steel composition. The system provides information that has not been available before, thus enabling more precise process planning, improvement of the consistency of products and better opportunities for future steel development.