A review is presented on: (i) topological indices (TIs) which are numbers derived from constitutional formulas and which have continuously evolved towards higher discriminating power and better correlating ability; (ii) stereochemical descriptors, allowing structures of diastereomers and enantiomers to be encoded in computer language. Uses of these descriptors include: structure encoding and retrieval; quantitative structure-activity relationships (QSAR) and computer-assisted drug design (CADD); creation and exploration of data bases; quantitative assessment of similarity and dissimilarity.