We briefly present in this short paper a new SIze REsolved Aerosol Model (S<small>IREAM</small>) which simulates the evolution of atmospheric aerosol by solving the General Dynamic Equation (GDE). S<small>IREAM</small> segregates the aerosol size distribution into sections and solves the GDE by splitting coagulation and condensation/evaporation-nucleation. A quasi-stationary sectional approach is used to describe the size distribution change due to condensation/evaporation, and a hybrid equilibrium/dynamical mass-transfer method has been developed to lower the computational burden. S<small>IREAM</small> uses the same physical parameterizations as those used in the Modal Aerosol Model, M<small>AM</small> Sartelet et al. (2006). It is hosted in the modeling system P<small>olyphemus</small> Mallet et al., 2007, but can be linked to any other three-dimensional Chemistry-Transport Model.