This volume represents the proceedings of the 24th Mos­ bach Colloquium on "Regulation of Transcription and Trans­ lation in Eukaryotes" which was held April 26-28, 1973, in Mosbach, Germany, under the auspices of the Gesellschaft fiir Biologische Chemie. To the three of us (H. KERSTEN, P. KARLSON and myself) who were commissioned with the invitation of speakers, it was a difficult decision as to whether we should attempt to cover with some twenty contributions as many aspects of this broad topic as possible, or to sacrifice the intellectually perhaps more pleasing but more specula­ tive concepts and to concentrate on a few aspects of gene expression in reasonable detail. We unanimously decided on the latter course, leaving such important and timely topics as for example, hormone action, cyclic AMP and reverse transcription to the proceedings of other symposia, and con­ centrating on the four questions which are most basic to an understanding of the mechanisms of transcription and trans­ lation and for which fragmentary but nonetheless reliable experimental results have become available within the last few years. These are the structure of chromatin, the syn­ thesis of messenger RNA, the structure of the active ribo­ some, and the role of initiation factors in protein synthesis.