A dynamic model for a semiautogenous grinding mill is developed in the standard dynamic system form of state and state-output equations and the resulting model is analyzed with this perspective. The model is based on results obtained under stationary conditions using a pilot SAG mill and communicated in an earlier paper. From the point of view of the state equations, these results constitute sub-models representing grinding, classification, transport, and power draw, which are functions of the mill state and input variables. These sub-models may be easily changed in this slate equation structure to accommodate new developments. Thanks to the form in which the model has been derived, it may be incorporated in a systematic way to grinding circuits. This model serves for the study by simulation of control strategies, either manual or automatic, as well as for testing estimators or soft-sensors for unmeasured variables. Results in accordance with real cases were obtained using the model for simulating some typical operating procedures.