The legal status of undercover investigations and techniques used in such investigations is confused. Many doctrines do, or may, relate to undercover police work, but judicial opinions and other discussions often suggest that the available legal "tools" are inadequate to address problems in undercover work. Taking into account this doctrinal chaos, each section of this chapter addresses a doctrine with the potential to affect under cover investigations. First, descriptions of several actual undercover investigations are presented in the format of "problems." The traditional law of entrapment is then reviewed followed by a discussion of the sixth amendment right to counsel and its effect upon the elicitation and overhearing by undercover personnel of self-incriminating admissions made by defendants. The chapter concludes with a discussion of the application of the fourth amendment's protection from unreasonable searches and seizures to undercover operations. Each section presents a relevant U.S. Supreme Court decision: United States v. Russell regarding entrapment, United States v. Henry regarding the elicitation of self-incriminating statements, and Hoffa v. United States concerning undercover surveillance as a "search." Notes on each case are included.