The first volume in this Methods Molecular Biology series, Proteins (1984), concentrated on basic techniques for the analysis and purification of peptides and proteins. As the series developed, more specialized volumes on proteins were introduced, such as those on Immunochemical Protocols (vol. 10), Practical Protein Chro- tography (vol. 11), Analysis Glycoprotein Biomedicine (vol. 14), Protein-DNA Interactions (vol. 30), Biomembrane Protocols (vols. 19 and 27), Analyses and Methods (vol. 17), and Optical Spectroscopy, Microscopy, and Macroscopic Techniques (vol. 22). Further specialist volumes on peptides, monoclonal antibodies, immunoassays, ELISA, protein engineering, protein stability, mass spectrometry of proteins, automated sequence analysis, and protein NMR are currently in preparation. Since it is now a decade since the initial volume was published, it seems an especially appropriate moment to extensively reorganize, update, and revise the earlier volume. In an attempt to be more c- prehensive in our coverage, this current volume, Basic Protein and Peptide Protocols, is totally committed to basic analytical methods; a planned companion volume will later concentrate on preparative techniques. Those analytical techniques requiring expensive speci- ized instrumentation, such as NMR, mass spectrometry, X-ray cr- tallography, spectroscopy, and automated sequence analysis, are not described here, but in the appropriate specialized volumes listed above.