We applied the molecular electrostatic field of a cluster model of the Si(111) reconstructed crystal surface as a reactivity map for the prediction of preferred adsorption sites of pointlike dipolar molecules. It was found that experimentally located preferred sites are correctly predicted by both molecular electrostatic field maps, as calculated by the semiempirical NDDO molecular orbital method with the AM1 parametrization, and results obtained by ab initio molecular orbital calculations with a split valence-shell basis set. It is thus probable that electrostatic field maps can be applied to other crystalline surfaces for the pictorial representation of reactivity properties, too.