One of the central problems in the study of the mechanism of DNA-ligand interactions is the existence and nature of sequence specificity with respect to the base pairs of DNA. The presence of such a specificity could be of particular significance because it might possibly mean the involvement of specific genes in the effectiveness of the different drugs. The elucidation of the factors responsible for the specificity could then be important for the development of compounds susceptible to contribute to the control of gene expression and also to the development of rationally conceived, improved new generations of effective and specific chemotherapeutic agents. Important recent achievements, experimental and theoretical, in the analysis of such sequence specificities open prospects for possible rapid progress in this field. The 23rd Jerusalem symposium was devoted to the exploration of these recent achievements in relation to many types of ligand, with special emphasis on antitumor drugs. All major types of interaction, intercalation, groove binding, covalent linking, coordination, have been considered. So was also the effect of the interaction on the structure and properties of the nucleic acids and the relationship between the interaction and biological or pharmacological activities. We feel that this Volume presents a relatively complete up-to-date account of the state of the art in this important field of research.