Many methods have been developed or adapted for the study of RNA processing, which plays a key role in the expression of genetic information. Volumes 180 and 181 of Methods in Enzymology, RNA Processing, Parts A and B, represent the first comprehensive collation of protocols used for the preparation of substrates, for the preparation of extracts and enzymes, and for the analysis of products in RNA processing. At least half of the chapters present techniques that are directly applicable to other areas of nucleic acid biochemistry and cell biology.Preparation of Substrates: Purification of RNA Molecules: S.L. Berger and J.M. Chirgwin, Isolation of RNA. T. Ikemura, Purification of RNA Molecules by Gel Techniques. N.K. Tanner, Purifying RNA by Column Chromatography. In Vitro Synthesis of RNA: J.K. Yisraeli and D.A. Melton, Synthesis of Long, Capped Transcripts in Vitro by SP6 and T7 RNA Polymerases. J.F. Milligan and O.C. Uhlenbeck, Synthesis of Small RNAs Using T7 RNA Polymerase. V.M. Reyes and J.N. Abelson, In Vitro Synthesis of End-Mature, Intron-Containing Transfer RNAs. In Vivo Preparation of Substrates: S. Chen-Kiang and D.J. Lavery, Preparation of Precursors to mRNA from Mammalian Cell Nuclei. S. Chen-Kiang and D.J. Lavery, Pulse Labeling of Heterogeneous Nuclear RNA in Isolated Nuclei. J. Klootwijk and R.J. Planta, Isolation and Characterization of Yeast Ribosomal RNA Precursors and Preribosomes. G. Knapp, Preparation of Yeast Transfer RNA Precursors in Vivo. Characterization of RNAs: Primary StructurlĂ&