This volume contains nineteen contributions on some of the most relevant topics in modern molecular biology and biochemistry presented by leading scientists of the USSR and Italy. One group of papers are mainly concerned with the structure and functions of the genetic elements in eukaryote cells; among the topics are the following: Nucleosome structure, characteriza- tion of the nuclear matrix, ribosomal gene organization, gene ex- pression during the cell cycle, and mapping of the mitochondrial transcripts. Several other aspects of macromolecule structure and function have been discussed: tRNA modification, translation fac- tors, RNA interaction with RNA-polymerase, DNA-dependent ATPases, proteins involved in active transport, enzyme induction, iron and sulfur proteins, etc. Furthermore, some studies on macromolecule changes in embryonic development and cell differentiation have been presented, including DNA methylation and macromolecular synthesis in sea urchins, polyribosomes in loach, and histone modifications in spermiogenesis. Finally, a stimulating and brilliant presenta- tion on protein--nucleic acid interaction by Professor Engelhardt closes the scientific contributions. The papers collected in this volume have been presented at the First Soviet-Italian Symposium on "Macromolecules in the Functioning Cell" sponsored by the Italian Society of Biochemistry, the USSR Academy of Sciences, and the Capri Center for Cell Biology and Natural Sciences, and supported mainly by the Italian National Research Council (CNR). The efforts of Professor A. Ruffo, as Chairman of the Scientific Committee, have to be particularly ack- nowledged as being instrumental in the success of the symposium.