This volume contains contributions from the speakers at the NATO Advanced Research Workshop on "3D 5tructure and Dynamics of RNA", which was held in Renesse, The Netherlands, 21 - 24 August, 1985. Two major developments have determined the progress of nucleic acid research during the last decade. First, manipulation of genetic material by recombinant DNA methodology has enabled detailed studies of the function of nucleic acids in vivo. 5econd, the use of powerful physical methods, such as X-ray diffraction and nuclear magnetic resonance spectroscopy, in the study of biomacromolecules has provided information regarding the structure and the dynamics of nucleic acids. Both developments were enabled by the advance of synthetic methods that allow preparation of nucleic acid molecules of required sequence and length. The basic understanding of nucleic acid function will ultimately depend on a close collaboration between molecular biologists and biophy­ sicists. In the case of RNA, the ground rules for the formation of secondary structure have been derived from physical studies of oligoribonucleotides. Powerfull spectroscopic techniques have revealed more details of ~~A structure including novel conformations (e.g. left-handed Z-RNA). A wealth of information has been obtained by studying the relatively small transfer RNA molecules. A few of these RNAs have been crystallized, enabling determination of their three-dimensional structure. It has become apparent that "non-classical" basepairing between distal nucleotides gives rise to tertiary interactions, determining the overall shape of the molecule.