The paper outlines a procedure to simulate a grinding-flotation plant. Population balance models are used to describe the grinding, classification and flotation processes. In the grinding and classification models particles are characterized by their size, while in the flotation models particles are characterized by their size and mineral composition. The link between the grinding and flotation circuits is made by an empirical model that generates the mineral-size particle population from the size distribution of the grinding circuit product. The simulator is calibrated using plant data collected from the Penoles-Fresnillo Pb-Ag concentrator in Mexico.