The regulation of gene expression has been studied traditionally at the level of transcription. While a few examples of translational regulation were known, they were considered interesting exceptions to the general rule of regulation at the level of RNA synthesis. However, over the last few years it has become evident that several widespread posttranscriptional, mostly cytoplasmic mechanisms have profound effects on gene expression. All of these mechanisms ultimately contribute to control protein synthesis, either directly, by affecting the rate of translation, or indirectly, by affecting the abundance of mRNA. Some of them exert a qualitative, all-or-none control, for example by complete repression or elimination of certain mRNAs, others determine the intracellular location or the cell-type in which a particular RNA is translated, and still others have a quantitative effect, controlling the amount of protein made from a certain mRNA. The analysis of some of the most exciting aspects of these cytoplasmic mechanisms of gene regulation is a major focus of the DFG Forschergruppe 855 "Cytoplasmic regulation of gene expression".