Group VII of the Landolt-Börnstein New Series is devoted to the physical properties of biological systems. It begins with volume VII/1 covering the nucleic acids which are of central importance in all processes involving gene expression. This field has become of practical consequence during the last decade through the development of genetic engineering. Because of the amount of the data available, volume VII/1 had to be divided into several subvolumes. The first two subvolumes, VII/1a and VII/1b, which appeared in 1988, deal with crystallographic and structural data which give a comprehensive information on the three-dimensional structure of the nucleic acids, their folding properties, their hydrogen bonding schemes, their metal binding capabilities, their hydration and their drug complexation. Subvolume VII/1c covers the first part of spectroscopic, kinetic and physical data; the present subvolume VII/1d concludes this chapter and also deals with theoretical investigations.