Just wanted to put my 2 cents in: A comma should be used after all items in a series (except the last). "I bought apples, oranges, and pears today. Words, phrases, or clauses that "match in grammatical form" and "importance" should be parallel. Agreeing with me are Simon & Schuster (Handbook for Writers), Shrunk and White (The elements of style), Prentice Hall (Handbook for Writers), APA (Publication Manual), MLA ( Handbook for Writers of Research Papers), Lunsford & Conners (The St. Martin's Handbook), and Lannon (Technical Writing). Disagreeing with me are (at least two) newspaper stylebooks, The Washington Post and Associated Press. Even though I turn to these stylebooks frequently, I stick with tradition for things like punctuation, as some of journalism style is based on space (I have no citation for this, but I do know that The Washington Post, at one point, dropped the second "e" from employee for this reason, but added it again after persistent complaints). How often do you see a comma following an introductory (adverbial) phrase when reading the morning paper? >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Portia Williams [log in to unmask] Division of English as an International Language University of Illinois at Urbana-Champaign