The role of topological indices in drug development research is updated. A series of definitions in the fields of topological indices and drug discovery technologies are introduced. In all cases where it is possible the IUPAC recommendations for terms used in medicinal chemistry and in computational drug design are used. Recent advances on the use of topological indices in the lead discovery process are reviewed making emphasis on two approaches: combined use of connectivity and charge indices and TOSSMODE approach. Studies of similarity/dissimilarity and rational combinatorial library design are also updated. The use of these descriptors in lead optimization process is critically analyzed. Topological indices QSAR, the problem of 2D QSAR versus 3D QSAR, strategies of orthogonalization and the use of linear combination and semiempirical connectivity indices are also described. The main directions of progress for these indices in QSAR and drug research are analyzed with examples of application of novel statistical techniques, such as artificial neural networks, genetic algorithms and partial least squares. Future outlooks of development in this area of research are also given.