This book is based on an advanced course of lectures on ribosome structure and protein biosynthesis that I offer at the Moscow State University. These lectures have been part of a general course on molecular biology for almost three decades, and they have undergone considerable evolution as knowledge has been pro- gressing in this field. The progress continues, and readers should be prepared that some facts, statements, and ideas included in the book may be incomplete or out- of-date. In any case, this is primarily a textbook, but not a comprehensive review. It provides a background of knowledge and current ideas in the field and gives ex- amples of observations and their interpretations. I understand that some interpre- tations and generalizations may be tentative or disputable, but I hope that this will stimulate thinking and discussing better than if I left white spots. The book has a prototype: it is my monograph "Ribosome Structure and Pro- tein Biosynthesis" published by the Benjamin/Cummings Publishing Company, Menlo Park, California, in 1986. Here I have basically kept the former order of pre- sentation ofthe topics and the subdivision into chapters. The contents ofthe chap- ters, however, have been significantly revised and supplemented. The newly writ- ten chapters on translational control in prokaryotes (Chapter 16) and eukaryotes (Chapter 17) are added.