  To contribute to the understanding of noncovalent binding of halogenated
molecules with a biological activity, electrostatic potential (ESP) maps of
more than 2,500 compounds were thoroughly analysed. A peculiar region of
positive ESP, called $\sigma$-hole, is a concept of central importance for
halogen bonding. We aim at simplifying the view on $\sigma$-holes and provide
general trends in organic drug-like molecules. The results are in fair
agreement with crystallographic surveys of small molecules as well as of
biomolecular complexes and attempt to improve the intuition of chemists when
dealing with halogenated compounds.
