The case law on attorney-client privilege is extensive and can be somewhat complex. Over seven hundred articles in Westlaw, for example, have the phrase "attorney-client privilege" in the title; in the last three years alone, there have been over 3700 federal cases in which the phrase "attorney-client privilege" appears at least once. However, business law and legal environment textbooks typically have a short or even no discussion of issues related to attorney-client privilege. This article presents three practical and easy-to-remember principles of attorney-client privilege that every business student should know and that every professor of business law could use in teaching classes in business law and legal environment. They are as follows: (1) The attorney-client privilege protects communications involving the legal advice of attorneys, not communications involving their business advice; (2) A client can lose the privilege by sharing an attorney's legal advice with a third party; and (3) Not all attorneys enjoy the same presumption that their confidential communication was made for the purpose of providing legal advice. While legal scholars and federal judges can be innovative in their thinking about privilege issues, these basic principles are unlikely to change abruptly because they are, well, "black letter law." For this reason, they are precisely what business students should know about attorney-client privilege. (Contains 70 footnotes.)