Do you find yourself on the PROWL for online protein analysis tools? (Hey, I have to take the easy puns where I can get them…) If so, then you need to scurry over to the website of the Chait laboratory at The Rockefeller University. This laboratory, dedicated to the development of “proteomic tools for dissecting cellular function, with a special emphasis on the mass spectrometry (MS) of peptides and proteins,” has compiled seven of its tools on the page entitled “PROWL.” These various tools allow users to do such things as predict peptide maps from protein sequence collections, analyze mass spectrometric fragmentations, find modifications on polypeptide sequences, and identify proteins that match tandem mass spectra. All of the tools are online, so they do not require downloading. There aren’t any tutorials, but the tools are all fairly straightforward, and in some instances, examples are provided.