Although the convective process of cloud electrification has been proposed long ago, there is a lack of numerical simulations in the literature that would put this mechanism to the test. A numerical model developed with the purpose of evaluating the electrification caused by the convective mechanism alone is presented. More precisely, in the model only the interaction between free ions and cloud and precipitation particles separates charge. The ability of this mechanism to reproduce the most important features of cloud electrification is discussed. The study is carried out on a slab symmetric domain of 16 km per side. The microphysics is represented by a bulk parameterization including four categories: cloud ice, cloud water, hail and rain. The model also includes aerosols and small ions, and it takes into account the difference in mobilities between positive and negative small ions. The influence of variables such as the number of particles, number of aerosols and ion pair formation rate is tested. A dipolar structure bounded by the cloud is obtained. The magnitude of electric field is too modest to produce any lightning after 10 min of simulation.¿ 1997 American Geophysical Union