A review. With the advances in genomics, proteomics and functional genomics new therapeutic targets to be tackled by medicinal chem. are expected. This article reviews applications of first principle methods to address medicinal chem. issue related to drug/target interactions. Two selected representative case studies involving therapeutically interesting targets are presented. The first case study presents how DFT can contribute to ameliorate scoring functions for drug screening in particular by enabling the discrimination between inhibitors and substrates. The second example shows the use of DFT within the framework of a QM/MM mixed approach for elucidating mechanisms of reaction. This approach allows defining the electronic state and structure of the reaction transition state whose knowledge is essential for designing potent and specific transition state analogs inhibitors. Finally, addressing the issue of other medicinal chem. related application of DFT we suggest that DFT has indeed the potentiality of becoming very important for challenging new issues presented to medicinal chem. in the post genomic era. [on SciFinder (R)]