A recent volume of this series (Signals and Signal Transduction Pathways in Plants (K. Palme, ed.) Plant Molecular Biology 26, 1237-1679) described the relay races by which signals are transported in plants from the sites of stimuli to the gene expression machinery of the cell. Part of this machinery, the transcription apparatus, has been well studied in the last two decades, and many important mechanisms controlling gene expression at the transcriptional level have been elucidated. However, control of gene expression is by no means complete once the RNA has been produced. Important regulatory devices determine the maturation and usage of mRNA and the fate of its translation product. Post-transcriptional regulation is especially important for generating a fast response to environmental and intracellular signals. This book summarizes recent progress in the area of post-transcriptional regulation of gene expression in plants. 18 chapters of the book address problems of RNA processing and stability, regulation of translation, protein folding and degradation, as well as intracellular and cell-to-cell transport of proteins and nucleic acids. Several chapters are devoted to the processes taking place in plant organelles.